Triaxial Magnetic Field Correction Coil, Physics Package, Physics Package for Optical Lattice Clock, Physics Package for Atomic Clock, Physics Package for Atom Interferometer, Physics Package for Quantum Information Processing Device, and Physics Package System

ABSTRACT

There is a need to maintain or enhance the magnetic field correction accuracy of a physics package while making the physics package more compact and portable. A triaxial magnetic field correction coil provided inside a vacuum chamber surrounding a clock transition space having atoms disposed therein. The triaxial magnetic field correction coil formed into a shape such that it is possible to correct, for magnetic field components of three axial directions passing through the clock transition space, a constant term, a first order spatial derivative term, a second order spatial derivative term, a third or higher order spatial derivative term, or some given combination of these terms. The triaxial magnetic field correction coil can be used in, for example, a physics package for an optical lattice clock.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the United States national phase of InternationalApplication No. PCT/JP2021/013473 filed Mar. 30, 2021, and claimspriority to Japanese Patent Application No. 2020-065311 filed Mar. 31,2020, the disclosures of which are hereby incorporated by reference intheir entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a triaxial magnetic field correctioncoil, a physics package, a physics package for an optical lattice clock,a physics package for an atomic clock, a physics package for an atominterferometer, a physics package for a quantum information processingdevice, and a physics package system.

Description of Related Art

Optical lattice clocks are atomic clocks proposed by KATORI Hidetoshi,who is one of the inventors of the present application. An opticallattice clock confines an atom population in an optical lattice formedby laser light, and measures the resonant frequency in a visible lightrange. Accordingly, optical lattice clocks can achieve 18-digit accuracymeasurement, which surpasses the accuracies of current cesium clocks.Optical lattice clocks have been eagerly researched and developed notonly by the group including the inventors but also by various groupsinside and outside of this country, and have been developed asnext-generation atomic clocks.

The latest technology of optical lattice clocks is described in thefollowing Patent Documents 1 to 3, for example. Patent Document 1describes that a one-dimensional moving optical lattice is formed in anoptical waveguide having a hollow pathway. Patent Document 2 describesan aspect of setting an effective magic frequency. Patent Document 3describes a radiation shield that reduces adverse effects of blackbodyradiation emitted from surrounding walls.

The optical lattice clock measures time with high accuracy. Accordingly,the optical lattice clock can detect an elevation difference of 1 cm onthe Earth based on the general relativistic effect due to the gravity,as a deviation in temporal progress. Accordingly, if the optical latticeclock is made transportable and usable in a field outside of alaboratory, it would be applicable to new geodetic technologies, such asunderground resource exploration, and detection of underground cavitiesand magma chambers. Optical lattice clocks are mass-produced, andinstalled at many locations, and temporal variation in gravitationalpotential is continuously monitored, which allows applications thatinclude detection of diastrophism, and spatial mapping of thegravitational field. Thus, optical lattice clocks are expected tocontribute to society as a new fundamental technology beyond the boundsof highly accurate time measurement.

The following Non Patent Documents 1 to 5 describe attempts to makeoptical lattice clocks transportable. For example, Non Patent Document 4describes a physics package of an optical lattice clock stored in aframe having a length of 99 cm, a width of 60 cm, and a height of 45 cm.In the physics package, an atomic oven, a Zeeman slower, and a vacuumchamber are arranged sequentially in the length direction. Outside ofthe vacuum chamber there are arranged a pair of square magnetic fieldcorrection coils measuring about 30 to 40 cm on a side, for each ofthree axes, in the length direction, the width direction, and the heightdirection. For the sake of clock transition spectroscopy of atoms in azero magnetic field, the magnetic field correction coils are used tocompensate the magnetic field distribution in an area around the atomsduring spectrometry.

CITATION LIST Patent Literature

-   Patent Document 1: JP 6206973 B-   Patent Literature 2: JP 2018-510494 A-   Patent Document 3: JP 2019-129166 A

Non Patent Literature

-   Non Patent Document 1: Stefan Vogt et al. “A transportable optical    lattice clock” Journal of Physics: Conference Series 723 012020,    2016-   Non Patent Document 2: S. B. Koller et al. “Transportable Optical    Lattice Clock with 7×10-17 Uncertainty” Physical review letters 118    073601, 2017-   Non Patent Document 3: William Bowden et al. “A Pyramid MOT with    Integrated Optical Cavities as a Cold Atom Platform for an Optical    Lattice Clock” Scientific Reports 9 11704, 2019-   Non Patent Document 4: S. Origlia et al. “Towards an Optical Clock    for Space: Compact, High-Performance Optical Lattice Clock based on    Bosonic Atoms” Physical Review A 98, 053443, 2018-   Non Patent Document 5: N. Poli et al. “Prospect for a Compact    Strontium Optical Lattice Clock” Proceedings of SPIE 6673, 2007

The optical lattice clocks described in the aforementioned Non PatentDocuments 1 to 5 have room for further improvement in miniaturizationand transportability, to facilitate transportation, installation, andthe like of the optical lattice clocks, and to improve utilization.

In particular, the conventionally used magnetic field correction coilsare a factor that prevent miniaturization of the physics packages ofoptical lattice clocks. Miniaturization or transportability is widelyrequired not only for optical lattice clocks but also for devices usedfor highly accurate quantum measurement.

SUMMARY OF THE INVENTION

An object of the present invention is to realize a triaxial magneticfield correction coil usable in a physics package that achieves bothminiaturization or transportability, and maintenance or improvement ofmagnetic field correction accuracy.

A triaxial magnetic field correction coil according to the presentinvention is provided in a vacuum chamber that encloses a clocktransition space in which atoms are arranged, the triaxial magneticfield correction coil being configured to have a shape capable ofcorrecting any of a constant term, a first order spatial derivativeterm, a second order spatial derivative term, and a three or higherorder spatial derivative term, or any combination of the terms.

A physics package according to the present invention includes: thetriaxial magnetic field correction coil; and the vacuum chamber.

According to an aspect of the present invention, the vacuum chamberincludes an inner wall formed to have a point-symmetric shape centeredin the clock transition space in a first axis among the three axes, andthe triaxial magnetic field correction coil includes a group of coilsthat is formed to have a point-symmetric shape centered in the clocktransition space in a direction of the first axis, and is arranged onthe inner wall or adjacent to the inner wall.

According to an aspect of the present invention, the triaxial magneticfield correction coil includes two or more groups of coils that havedifferent coil sizes, coil shapes, or distances in the first axis.

An aspect of the present invention further includes a holder that has asparse structure and is detachably attached around the inner wall of thevacuum chamber, wherein the group of coils is attached to the holder.

According to an aspect of the present invention, the vacuum chamber isformed to have a point-symmetric shape centered in the clock transitionspace in a second axis that is an axis other than the first axis amongthe three axes, and the triaxial magnetic field correction coil includesa group of coils that is formed to have a point-symmetric shape centeredin the clock transition space in a direction of the second axis, and isarranged on the inner wall or adjacent to the inner wall.

According to an aspect of the present invention, the vacuum chamber isformed to have a point-symmetric shape centered in the clock transitionspace in a third axis that is an axis other than the first axis and thesecond axis among the three axes, and the triaxial magnetic fieldcorrection coil includes a group of coils that is formed to have apoint-symmetric shape centered in the clock transition space in adirection of the third axis, and is arranged on the inner wall oradjacent to the inner wall.

According to an aspect of the present invention, the vacuum chamber isformed to have a substantially cylindrical shape allowing the clocktransition space to be disposed on a central axis of the cylinder.

According to an aspect of the present invention, the vacuum chamber isformed to have a substantially spherical shape allowing the clocktransition space to be disposed at a center of the sphere.

According to an aspect of the present invention, at least a pair ofwalls of the vacuum chamber that face with each other have substantiallysquare shapes, and the clock transition space is formed to have asubstantially rectangular shape arranged on an axis connecting centersof the pair of squares.

According to an aspect of the present invention, at least part of thegroup of coils is formed on a flexible printed board, and is attached tothe inner wall formed to have the point-symmetric shape or to a holderformed to have a point-symmetric shape around the inner wall.

According to an aspect of the present invention, the physics packagefurther includes: a pair of MOT coils that are provided in the vacuumchamber, form a gradient magnetic field, and capture the atoms in acapture space of the MOT device; a bias coil that is provided in thevacuum chamber, and is for generating a bias magnetic field at aposition where the atoms are captured; and movement means for moving theatoms captured in the capture space to the clock transition space by amoving optical lattice, and at least part of the triaxial magnetic fieldcorrection coil is supported by a supporter that supports the MOT coils.

According to an aspect of the present invention, an optical resonatorthat includes an optical mirror that forms an optical lattice isprovided around the clock transition space in the vacuum chamber, and atleast part of the triaxial magnetic field correction coil is provided inthe optical resonator.

According to an aspect of the present invention, at least part of thetriaxial magnetic field correction coil is provided around an inner wallof the vacuum chamber.

A physics package system of the present invention includes: the triaxialmagnetic field correction coil; and a control device that controlscurrent that flows to the triaxial magnetic field correction coil.

The physics package according to the present invention may be used as aphysics package for an optical lattice clock, a physics package for anatomic clock, a physics package for an atom interferometer, and aphysics package for a quantum information processing device for atoms orionized atoms.

An aspect of the present invention further includes at least one atomiclaser cooling technology device among a Zeeman slower, a magneto-opticaltrap, and an optical lattice trap that guide the atoms into the clocktransition space.

The present invention can facilitate miniaturization or achievement oftransportability of a physics package including a clock transition spacein a vacuum chamber, and maintain or improve the accuracy of magneticfield correction.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 schematically shows an overall configuration of an opticallattice clock according to an embodiment.

FIG. 2 shows a schematic configuration of a physics package of theoptical lattice clock.

FIG. 3 schematically shows the appearance of the physics package.

FIG. 4 is a partially perspective view of the inside of the physicspackage in FIG. 3 .

FIG. 5 shows an overall shape of a triaxial magnetic field correctioncoil.

FIG. 6 shows a shape of a first coil group of an X-axis magnetic fieldcorrection coil.

FIG. 7 shows a shape of a second coil group of the X-axis magnetic fieldcorrection coil.

FIG. 8 shows a shape of a first coil group of a Y-axis magnetic fieldcorrection coil.

FIG. 9 shows a shape of a second coil group of the Y-axis magnetic fieldcorrection coil.

FIG. 10 shows a shape of a first coil group of a Z-axis magnetic fieldcorrection coil.

FIG. 11 shows a shape of a second coil group of the Z-axis magneticfield correction coil.

FIG. 12 shows a shape of a holder of the triaxial magnetic fieldcorrection coil.

FIG. 13 shows an example of a correction coil using a flexible printedboard.

FIG. 14 shows an example of a cylindrical correction coil using aflexible printed board.

FIG. 15 shows an example of currents flowing in the correction coil.

FIG. 16 shows flows of currents equivalent to those in the correctioncoil in FIG. 15 .

FIG. 17 shows another example of currents flowing in the correctioncoil.

FIG. 18 shows flows of currents equivalent to those in the correctioncoil in FIG. 17 .

FIG. 19 shows another example of a correction coil using a flexibleprinted board.

FIG. 20 shows a physics package that includes a spherical vacuumchamber.

FIG. 21 shows another installation example of a triaxial magnetic fieldcorrection coil.

FIG. 22 illustrates a mode of supporting the triaxial magnetic fieldcorrection coil in FIG. 21 .

FIG. 23A schematically shows a mode of correcting magnetic fields.

FIG. 23B schematically shows a mode of correcting magnetic fields.

FIG. 24 is a flowchart of calibration of the triaxial magnetic fieldcorrection coil.

FIG. 25 is a flowchart showing procedures of correcting the triaxialmagnetic field correction coil.

FIG. 26 schematically shows another mode of correcting magnetic fields.

FIG. 27 shows compensation of a stray magnetic field in a refrigerator.

FIG. 28 is a sectional view showing structures of a Zeeman slower and aMOT device.

FIG. 29 is a sectional view illustrating a void of a coil.

FIG. 30 shows a magnetic field distribution corresponding to theconfiguration in FIG. 28 .

FIG. 31A is a sectional view showing structures of a Zeeman slower and aMOT device.

FIG. 31B is a sectional view showing structures of the Zeeman slower andthe MOT device.

FIG. 32 shows a magnetic field distribution corresponding to theconfiguration in FIGS. 31A and 31B.

FIG. 33A shows a structure of a modified mode in FIGS. 31A and 31B.

FIG. 33B shows a structure of a modified mode in FIGS. 31A and 31B.

FIG. 34 is a sectional view of a Zeeman coil having a constant coilouter diameter.

FIG. 35A is a sectional view showing encapsulation of a coil for aZeeman slower.

FIG. 35B is a sectional view showing encapsulation of the coil for theZeeman slower.

DESCRIPTION OF THE INVENTION

(1) Schematic Configuration of Physics Package

FIG. 1 schematically shows an overall configuration of an opticallattice clock 10. The optical lattice clock included a physics package12, an optical system device 14, a control device 16, and a PC (PersonalComputer) 18, which are combined with each other.

As described in detail next, the physics package 12 is a device thatcaptures an atom population, confines them in an optical lattice, andcauses clock transitions. The optical system device 14 is a device thatincludes optical devices, such as a laser emission device, a laserreceiver device, and a laser spectrometer. The optical system device 14not only emits a laser and transmits the laser to the physics package12, but also performs processes of receiving light emitted by clocktransitions of the atom population in the physics package 12, convertingit into an electric signal, and dividing the signal into frequencybands. The control device 16 is a device that controls the physicspackage 12 and the optical system device 14. The control device 16 is acomputer dedicated to the optical lattice clock 10, and operates bysoftware controlling computer hardware including processors andmemories. For example, the control device 16 performs not only operationcontrol of the physics package 12 and operation control of the opticalsystem device 14, but also analysis processes, such as frequencyanalysis of clock transition obtained by measurement. The physicspackage 12, the optical system device 14, and the control device 16mutually, closely cooperate with each other and form the optical latticeclock 10.

The PC 18 is a general-purpose computer, and operates by softwarecontrolling computer hardware including processors and memories. Anapplication program for controlling the optical lattice clock 10 isinstalled in the PC 18. The PC 18 is connected to the control device 16,and not only controls the control device 16, but also entirely controlsthe optical lattice clock 10, which includes the physics package 12 andthe optical system device 14. The PC 18 serves as a UI (User Interface)of the optical lattice clock 10. A user can activate the optical latticeclock 10, and perform time measurement and verification of results,through the PC 18. In this embodiment, description is given mainly onthe physics package 12. Note that the physics package 12 and theincluded components required to control this package are sometimescollectively called a physics package system. The components requiredfor control are included in the control device 16 or the PC 18 in somecases, and are included in the physics package 12 itself.

FIG. 2 schematically shows the physics package 12 of the optical latticeclock according to the embodiment. FIG. 3 schematically shows an exampleof the appearance of the physics package 12. FIG. 4 is a partiallyperspective view of the internal structure of the physics package 12shown in FIG. 3 . FIGS. 2 to 4 (and the diagrams thereafter) show an XYZorthogonal rectilinear coordinate system having an origin in a targetspace (clock transition space 52) where atoms mentioned later can resideduring clock transition spectroscopy.

The physics package 12 includes a vacuum chamber 20, an atomic oven 40,a coil 44 for a Zeeman slower, an optical resonator 46, a coil 48 for aMOT (Magneto-Optical Trap) device, a cryostat reservoir 54, a thermallink member 56, a refrigerator 58, a vacuum pump main body 60, and avacuum pump cartridge 62.

The vacuum chamber 20 is a case that maintains the main part of thephysics package 12 at vacuum, and is formed to have a substantiallycylindrical shape. In particular, the vacuum chamber 20 includes a mainbody 22 formed to have a large substantially cylindrical shape, and aprotruding portion 30 formed to have a small substantially cylindricalshape that protrudes from the main body 22. The main body 22 is aportion that internally stores the optical resonator 46 to be describedlater and the like. The main body 22 includes a cylindrical wall 24 thatserves as a side surface of the cylinder, and a front circular wall 26and a rear circular wall 28 which serve as circular surfaces of thecylinder. The front circular wall 26 is a wall provided with theprotruding portion 30. The rear circular wall 28 is a wall opposite tothe protruding portion 30, and has a shape with a larger diameter thanthat of the cylindrical wall 24.

The protruding portion 30 includes a cylindrical wall 32 serving as aside surface of the cylinder, and a front circular wall 34. The frontcircular wall 34 is a circular surface remote from the main body 22. Aportion of the protruding portion 30 adjacent to the main body 22 had analmost open shape, is connected to the main body 22, and has no wallpart.

The vacuum chamber 20 is arranged so that the central axis (called aZ-axis) of the cylinder of the main body 22 is substantially horizontal.The central axis (this axis serves as a beam axis) of the cylinder ofthe protruding portion 30 extends in parallel with the Z-axis above theZ-axis in the vertically upward direction.

The vacuum chamber 20 is assumed to be formed to be, for example, about35 cm or less in the Z-axis direction, and about 20 cm or less in theX-axis direction and the Y-axis direction. Further miniaturization isalso assumed so as to be about 30 cm or less, about 25 cm or less, orabout 20 cm or less in the Z-axis direction. Also in the X-axisdirection and the Y direction, it is assumed to be about 15 cm or less,or about 10 cm or less. The distance between the beam axis and theZ-axis is configured to be, for example, about 10 to 20 mm.

In the embodiment, four legs 38 are provided around the four corners atthe lower part of the main body 22 of the vacuum chamber 20, and supportthe vacuum chamber 20. The vacuum chamber 20 is made sufficiently robustfrom metal, such as SUS (stainless steel), so as to withstand differencein air pressure when the inside becomes vacuum. The vacuum chamber 20 isformed so that the rear circular wall 28 and the front circular wall 34are detachable. These walls are detached at maintenance check.

The atomic oven 40 is a device provided around the distal end of theprotruding portion 30. The atomic oven 40 causes a heater to heat anarranged solid metal, emits, through a pore, atoms ejected from themetal owing to thermal agitation, and forms an atom beam 42. The beamaxis on which the atom beam 42 passes is configured in parallel with theZ-axis, and is configured to intersect with the X-axis at a positionslightly apart from the origin. The intersecting position corresponds toa capture space 50 that is a minute space where atoms to be describedlater are captured. The atomic oven 40 is basically provided in thevacuum chamber 20. However, its heat radiator extends to the outside ofthe vacuum chamber 20 for cooling. The atomic oven 40 heats the metal toabout 750K, for example. As the metal, for example, any of strontium,mercury, cadmium, ytterbium, and the like may be selected. However,there is no limitation thereto.

The coil 44 for the Zeeman slower is arranged on the downstream side ofthe beam axis of the atomic oven 40, from the protruding portion 30 tothe main body 22 of the vacuum chamber 20. The coil 44 for the Zeemanslower is a device made by integrally including a Zeeman slower thatdecelerates the atoms of the atom beam 42, and a MOT device thatcaptures the decelerated atoms. Both the Zeeman slower and the MOTdevice are devices based on an atomic laser cooling technology. The coil44 for the Zeeman slower shown in FIG. 2 is provided with a Zeeman coilused for the Zeeman slower, and one of a pair of MOT coils used for theMOT device, as a series of coils. Although clear classification cannotbe made, the large portion from the upstream to the downstreamcorresponds to the Zeeman coil that generates a magnetic fieldcontributing to the Zeeman slowing method, and the furthest downstreamside corresponds to the MOT coil that generates a gradient magneticfield contributing to the MOT method.

In the illustrated example, the Zeeman coil is of a decreasing type thathas a larger number of turns on the upstream side and a smaller numberof turns on the downstream side. The coil 44 for the Zeeman slower isaxisymmetrically arranged around the beam axis so that the atom beam 42passes through the inside of the Zeeman coil and the MOT coil. In theZeeman coil, a magnetic field caused to have a spatial gradient isformed, and emission of a Zeeman slower optical beam 82 deceleratesatoms.

The optical resonator 46 is a cylindrical component arranged around theZ-axis, and enables formation of an optical lattice therein. Multipleoptical components are installed in the optical resonator 46. One pairof optical mirrors on the X-axis, and another pair of optical mirrors inparallel therewith are provided, and optical lattice light is multiplyreflected between the total four mirrors, thus generating abow-tie-shaped optical lattice resonator. The atom population capturedin the capture space 50 is confined in the optical lattice. When therelative frequencies of two optical lattice light beams (clockwise andcounterclockwise) caused to enter the optical resonator 46 are shifted,this resonator forms a moving optical lattice that causes the standingwave of the optical lattice to move. The moving optical lattice movesthe atom population to the clock transition space 52. In the embodiment,an optical lattice including the moving optical lattice is configured tobe formed on the X-axis. Note that there may be adopted atwo-dimensional or three-dimensional optical lattice with a latticearranged not only on the X-axis but also on one or both of the Y-axisand the Z-axis. Thus, the optical resonator 46 can be called an opticallattice formation portion forming an optical lattice. The opticalresonator 46 is also a device based on atomic laser cooling technology.

The coil 48 for the MOT device generates a gradient magnetic field forthe capture space 50. The MOT device emits MOT light beams respectivelyalong three, or the X, Y, and Z axes, in a space where the gradientmagnetic field is formed. Accordingly, the MOT device captures atoms inthe capture space 50. The capture space 50 is configured on the X-axis.The coil 44 for the Zeeman slower shown in FIG. 2 is provided with aZeeman coil used for the Zeeman slower, and one of the pair of MOT coilsused for the MOT device, as a series of coils. In this diagram, thegradient magnetic field that contributes to the MOT method is generatedintegrally by the coil 48 for the MOT device and part of the coil 44 forthe Zeeman slower.

The cryostat reservoir 54 is formed so as to enclose the clocktransition space 52, and kept the inner space at a low temperature.Accordingly, in an inner space, blackbody radiation decreases. Thethermal link member 56 serving also as a support structure is attachedto the cryostat reservoir 54. The thermal link member 56 transfers heatfrom the cryostat reservoir 54 to the refrigerator 58. The refrigerator58 keeps the cryostat reservoir 54 at a low temperature via the thermallink member 56. The refrigerator 58 includes a Peltier element, andcools the cryostat reservoir 54 to about 190K, for example.

The vacuum pump main body 60 and the vacuum pump cartridge 62 aredevices for vacuumizing the vacuum chamber 20. The vacuum pump main body60 and the vacuum pump cartridge 62 are devices for subsequentlyvacuumizing the vacuum chamber 20. The vacuum pump main body 60 isprovided outside of the vacuum chamber 20. The vacuum pump cartridge 62is provided in the vacuum chamber 20. At the start of activation, thevacuum pump cartridge 62 is heated by a heater provided at the vacuumpump main body 60 and is activated. Accordingly, the vacuum pumpcartridge 62 is activated, and absorbs atoms, thus achieving a vacuum.

The vacuum pump cartridge 62 is installed in the main body 22 so as tobe in parallel with the coil 44 for the Zeeman slower. The coil 44 forthe Zeeman slower is arranged along the beam axis decentered in theX-axis direction from the central axis of the cylinder of the main body22. Accordingly, there is a relatively large space on the opposite sideaway from the direction in which the coil 44 for the Zeeman slower iseccentrically arranged. The vacuum pump cartridge 62 is installed inthis space.

The physics package 12 includes, as components of the optical system:vacuum-resistant optical windows 64 and 66 for optical lattice light; avacuum-resistant optical window 68 for MOT light; vacuum-resistantoptical windows 70 and 72 for Zeeman slower light and MOT light; andoptical mirrors 74 and 76.

The vacuum-resistant optical windows 64 and 66 for optical lattice arevacuum-resistant optical windows provided on opposite cylindrical walls24 of the main body 22 of the vacuum chamber 20 so as to face eachother. The vacuum-resistant optical window 64 and 66 for optical latticelight are provided so as to allow optical lattice light to enter and beemitted therethrough.

The vacuum-resistant optical window 68 for MOT light is provided so asto allow entry and emission therethrough of MOT light beams on two axes,among MOT light beams on the three axes used for the MOT device.

The vacuum-resistant optical windows 70 and 72 for Zeeman slower lightand MOT light are provided so as to allow Zeeman slower light and MOTlight on one axis to enter and be emitted therethrough.

The optical mirrors 74 and 76 are provided so as to change thedirections of the Zeeman slower light and the MOT light on the one axis.

The physics package includes, as components for cooling: a cooler 90 foran atomic oven; a cooler 92 for a Zeeman slower; and a cooler 94 for aMOT device.

The cooler 90 for the atomic oven is a water-cooling device that coolsthe atomic oven 40. The cooler 90 for the atomic oven is providedoutside of the vacuum chamber 20, and cools a radiator of the atomicoven 40, the radiator extending outside of the vacuum chamber 20. Thecooler 90 for the atomic oven includes a water-cooling tube that is atube made of metal and is for cooling, and causes cooling water to flow,which is a liquid coolant, in the tube, thus cooling the vacuum chamber20.

The cooler 92 for the Zeeman slower is a device that is provided on thewall part of the vacuum chamber 20, and cools the coil 44 for the Zeemanslower. The cooler 92 for the Zeeman slower includes a tube made of ametal, and flows cooling water in the tube, thus removing Joule heatgenerated at the coil 44 for the Zeeman slower.

The cooler 94 for the MOT device is a heat radiator provided on thecircular wall part of the vacuum chamber 20. At the coil 48 for the MOTdevice, Joule heat is generated, although the Joule heat is smaller inamount (e.g., about 1/10) than that of the cooler 92 for the Zeemanslower. Accordingly, the metal of the cooler 94 for the MOT deviceextends to the outside of the vacuum chamber 20 from the coil 48 for theMOT device, and radiates heat to the atmosphere.

The physics package 12 further includes, as components for correcting amagnetic field: a triaxial magnetic field correction coil 96; avacuum-resistant electric connector 98; an individual magnetic fieldcompensation coil 102 for a refrigerator; and an individual magneticfield compensation coil 104 for the atomic oven.

The triaxial magnetic field correction coil 96 is a coil for uniformlynullifying the magnetic field in the clock transition space 52. Thetriaxial magnetic field correction coil 96 is formed to have athree-dimensional shape so as to correct the magnetic field in thethree, or X, Y, and Z, axes. In the example shown in FIG. 4 , thetriaxial magnetic field correction coil 96 is formed to have asubstantially cylindrical shape as a whole. Each of coils constitutingthe triaxial magnetic field correction coil 96 is formed to have apoint-symmetric shape centered in the clock transition space 52 in eachaxis direction.

The vacuum-resistant electric connector 98 is a connector for supplyingelectric power to the inside of the vacuum chamber 20, and is providedon the circular wall part of the vacuum chamber 20. From thevacuum-resistant electric connector 98, power is supplied to the coil 44for the Zeeman slower, the coil 48 for the MOT device, and the triaxialmagnetic field correction coil 96.

The individual magnetic field compensation coil 102 for the refrigeratoris a coil for compensating the stray magnetic field from therefrigerator 58 that cools the cryostat reservoir 54. The Peltierelement included in the refrigerator 58 is a large current device whererelatively large current flows, and generates a large magnetic field.Around the Peltier element, the magnetic field is shielded by a highpermeability material. However, shielding is not completely achieved,and part of the magnetic field leaks. Accordingly, the individualmagnetic field compensation coil 102 for the refrigerator is configuredso as to compensate the stray magnetic field in the clock transitionspace 52.

The individual magnetic field compensation coil 104 for the atomic ovenis a coil for compensating the stray magnetic field from the heater ofthe atomic oven 40. The heater of the atomic oven 40 is also a largecurrent device, and the stray magnetic field cannot be ignored in somecases even with shielding by a high permeability material. For example,even in a case where a heater circuit is made of noninductive winding,an induced component remains in actuality, in wiring via a wiringterminal and an insulating layer. For example, even if the atomic ovenis covered with a high permeability material to facilitate magneticshielding, a part cannot be covered in actuality, such as an opening ofthe atom beam. Accordingly, the individual magnetic field compensationcoil 104 for the atomic oven is configured so as to compensate the straymagnetic field in the clock transition space 52.

(2) Operation of Physics Package

The basic operation of the physics package 12 is described. In thephysics package 12, the vacuum pump cartridge 62 included in the vacuumchamber 20 absorbs atoms, thus vacuumizing the inside of the vacuumchamber 20. Accordingly, for example, the inside of the vacuum chamber20 is in a vacuum state of about 10⁻⁸ Pa, which eliminates the effect ofair components, such as nitrogen and oxygen. Depending on the type ofthe vacuum pump to be used, a preprocess is preliminarily executed. Forexample, for a non-evaporable getter pump (NEG pump) and an ion pump,rough pumping is required to be performed from the atmosphere to acertain degree of vacuum before their operation. In this case, a roughpumping port is provided for the vacuum chamber, and rough pumping issufficiently performed through the port using a turbomolecular pump, forexample. For example, in a case of using an NEG pump as the vacuum pumpmain body 60, a step of activation of heating to a high temperature in avacuum is required to be preliminarily executed.

In the atomic oven 40, the metal is heated by the heater to a hightemperature, and atomic vapor w is generated. The atomic vapor emittedfrom the metal in this process sequentially passes through the pore, isconverged, translates, and forms an atom beam 42. The atomic oven 40 isinstalled so as to form the atom beam 42 on the beam axis in parallelwith the Z-axis. Note that in the atomic oven 40, an atomic oven mainbody is heated by a heater. However, the atomic oven main body and ajoint that supports this main body are thermally insulated via a thermalinsulator. Furthermore, a joint connected to the physics package iscooled by the cooler 90 for the atomic oven, thus preventing the physicspackage 12 from being affected by a high temperature, or reducing theadverse effect of the high temperature.

The coil 44 for the Zeeman slower is installed so as to beaxisymmetrical with respect to the beam axis. The inside of the coil 44for the Zeeman slower is irradiated with the Zeeman slower optical beam82 and the MOT optical beam 84 on one axis. The Zeeman slower opticalbeam 82 enters from the vacuum-resistant optical window 70 for Zeemanslower light and MOT light, and is reflected by the optical mirror 74installed downstream of the beam away from the coil 48 for the MOT.Accordingly, the Zeeman slower optical beam 82 is overlaid on the atombeam 42, and travels upstream of the beam axis in parallel to the beamaxis. In this process, owing to the effect of the Zeeman splittingproportional to the intensity of the magnetic field and the effect ofthe Doppler shift, the atoms in the atom beam 42 absorb the Zeemanslower light, are given momentum in the deceleration direction, and aredecelerated. The Zeeman slower light is reflected upstream of the coil44 for the Zeeman slower by the optical mirror 76 disposed aside of thebeam axis, and is emitted through the vacuum-resistant optical window 72for Zeeman slower light and MOT light. Note that the coil 44 for theZeeman slower generates Joule heat. However, cooling is performed by thecooler 92 for the Zeeman slower. Accordingly, the temperature isprevented from being high.

The sufficiently decelerated atom beam 42 reaches the MOT device thatincludes the MOT coil on the furthest downstream side of the coil 44 forthe Zeeman slower, and the coil 48 for the MOT device. In the MOTdevice, a magnetic field having a linear spatial gradient is formedcentered in the capture space 50. The MOT device is irradiated with MOTlight in the three-axis directions, on the positive and negative sides.

The MOT optical beam 84 in the Z-axis direction is emitted in thenegative direction of the Z-axis, and is then reflected outside of thevacuum-resistant optical window 72 for Zeeman slower light and MOTlight, thus being emitted also in the positive direction of the Z-axis.MOT optical beams 86 a and 86 b on the remaining two axes are emittedinto the MOT device through the vacuum-resistant optical window 68 forMOT light and by an optical mirror, not shown. As shown in FIG. 4 ,these two axes are in two directions perpendicular to the Z-axis andinclined respectively from the X-axis and the Y-axis by 45 degrees;emission is performed in these two directions. The configurationallowing the two MOT optical beams 86 a and 86 b to be perpendicular tothe Z-axis is capable of narrowing the distance between the coil 44 forthe Zeeman slower and the coil 48 for the MOT device, thus contributingto miniaturization of the vacuum chamber 20. In a case where thedirections of emission of the MOT optical beams are configured to beinclined respectively from the Z-axis and the Y-axis by 45 degrees, thedistance in the beam axis is required to be large so as to prevent theMOT optical beams from interfering with the Zeeman slower and thecryostat reservoir. In this case, the device size is larger than in thecase where the two axes of the MOT light beams are perpendicular to theZ-axis.

In the MOT device, the atom beam receives a restoring force centered inthe capture space 50 by the magnetic field gradient and is decelerated.Accordingly, the atom population is captured in the capture space 50.Note that the position of the capture space 50 can be finely adjusted byadjusting the offset values for the magnetic field to be generated bythe triaxial magnetic field correction coil 96. The Joule heat generatedat the coil 48 for the MOT device is discharged outside of the vacuumchamber 20 by the cooler 94 for the MOT device.

An optical lattice light beam 80 enters in the X-axis direction throughthe vacuum-resistant optical window 64 for optical lattice light towardthe vacuum-resistant optical window 66 for optical lattice light. On theX-axis, the optical resonator 46 including two optical mirrors isinstalled, and causes reflection. Accordingly, on the X-axis there isformed an optical lattice potential with a series of standing waves inthe X-axis direction in the optical resonator 46. The atom population iscaptured by the optical lattice potential.

The optical lattice can be moved along the X-axis by slightly changingthe wavelength. By movement means through the moving optical lattice,the atom population is moved to the clock transition space 52. As aresult, the clock transition space 52 is apart from the beam axis of theatom beam 42. Accordingly, the effects of blackbody radiation emittedfrom the atomic oven 40 at a high temperature can be removed. The clocktransition space 52 is enclosed by the cryostat reservoir 54, and isshielded from blackbody radiation emitted from ambient materials atordinary temperatures. In general, blackbody radiation is proportionalto the fourth power of the absolute temperature of a material.Accordingly, reduction in temperature by the cryostat reservoir 54exerts a large advantageous effect of removing the impact of theblackbody radiation.

In the clock transition space 52, atoms are irradiated with laser lightwhose optical frequency is under control, highly accurate spectroscopyof clock transitions (i.e., resonance transitions of atoms serving asthe reference of the clock) is performed, and the frequency that isspecific to the atom and invariant is measured. Thus, an accurate atomicclock is achieved. Improvement of the accuracy of the atomic clockrequires removal of perturbation around the atoms, and the frequency isaccurately read. It is particularly important to remove the frequencyshift caused by the Doppler effect due to the thermal agitation of theatoms. In the optical lattice clock, the atom movement is frozen byconfining the atoms in a space sufficiently smaller than the wavelengthof the clock laser by the optical lattice created by interference of thelaser light. Meanwhile, in the optical lattice, the frequencies of atomsare shifted by laser light that forms the optical lattice. For theoptical lattice light beam 80, a specific wavelength or frequency called“magic wavelength” or “magic frequency” is selected, which removes theeffects of the optical lattice to the resonant frequency.

Furthermore, the clock transitions are also affected by a magneticfield. Atoms in the magnetic field cause Zeeman splitting dependent onthe intensity of the magnetic field. Accordingly, the clock transitionscannot accurately measured. In the clock transition space 52, themagnetic field is corrected so as to equalize and nullify the magneticfield. First, a stray magnetic field caused by the Peltier element ofthe refrigerator 58 is dynamically compensated by the individualmagnetic field compensation coil 102 for the refrigerator that generatesa compensation magnetic field dependent on the intensity of the straymagnetic field. Likewise, it is configured so that the stray magneticfield caused by the heater of the atomic oven 40 can be dynamicallycompensated by the individual magnetic field compensation coil 104 forthe atomic oven. Note that for the coil 44 for the Zeeman slower and thecoil 48 for the MOT device, the current signal is turned off at timingof measurement of the frequency of clock transition, and energization isnot performed, thus preventing effects of the magnetic field. Themagnetic field of the clock transition space 52 is further corrected bythe triaxial magnetic field correction coil 96. The triaxial magneticfield correction coil 96 includes multiple coils in each axis, and canremove not only uniform components of the magnetic field but alsospatially varying components.

Thus, in the state where the disturbances are removed, the atompopulation is urged to be subjected to clock transition by laser light.Light emitted as a result of the clock transition is received by theoptical system device, subjected to a spectroscopic process and the likeby the control device, and the frequency is obtained. Hereinafter,embodiments of the physics package 12 are described in detail.

(3) Shape and Installation Mode of Magnetic Field Correction Coil

By reference to FIGS. 5 to 11 , the triaxial magnetic field correctioncoil 96 in the physics package 12 is described. Here, the triaxialmagnetic field correction coil 96 is assumed to be formed to have apredetermined shape by winding a covered conductor wire that includes aconducive wire made of copper or the like and having been subjected toan insulating process with a polyimide resin.

FIG. 5 is a perspective view showing all the coils of the triaxialmagnetic field correction coil 96. FIGS. 6 to 11 are perspective viewsshowing individual coils that constitute the triaxial magnetic fieldcorrection coil. The triaxial magnetic field correction coil 96 isattached around an inner wall of the main body 22 of the vacuum chamber20. Accordingly, the triaxial magnetic field correction coil 96 isformed to have a substantially cylindrical shape centered in the clocktransition space 52. The triaxial magnetic field correction coil 96includes a first coil group and a second coil group in each of thedirections of the X-axis, Y-axis, and Z-axis.

FIG. 6 shows a first coil group 120 in the X-axis direction (a directionin which an optical lattice in one axis is formed, and the movingoptical lattice moves). The first coil group 120 includes two coils 122and 124 installed apart from each other by a distance c in the X-axisdirection centered in the clock transition space 52. The coils 122 and124 are each formed to have a rectangular shape with the length of theside in the Y-axis direction being a, and the length of the side in theZ-axis direction being b. The coils 122 and 124 are formed to have apoint-symmetric shape with respect to the clock transition space 52.

The first coil group 120 causes the coils 122 and 124 to constitute asquare-shaped Helmholtz-type coil so as to substantially uniformlygenerate the magnetic field at a central part in the X-axis direction.The square-shaped Helmholtz-type coil includes the coils 122 and 124formed to have a square shape with a=b, with c/2a= about 0.5445. Whencurrents having the same magnitude flow in the same direction, the coils122 and 124 serve as a Helmholtz-type coil pair that forms a magneticfield having high uniformity in the X-axis direction. However, in theembodiment, currents having different magnitudes and directions areallowed to flow through the coils 122 and 124. Note that the coils 122and 124 can sufficiently improve the uniformly of the magnetic fieldeven in a case of a≠b. In a case of a>b, the deviation of the magneticfield distribution in the Y-axis direction tends to be smaller than thatof the magnetic field distribution in the Z-axis direction. In a case ofa<b, the deviation of the magnetic field distribution in the Z-axisdirection tends to be smaller than that of the magnetic fielddistribution in the Y-axis direction. In the case of a≠b, and where c isoptimized is called a rectangular Helmholtz-type coil. The first coilgroup 120 may be configured as a rectangular Helmholtz-type coil.

The first coil group 120 is used to adjust the value of the magneticfield component in the X-axis direction, and its first order spatialderivative term in the X-axis direction. First, 1) when currents havingthe same magnitude flow in the same direction through the coils 122 and124, a uniform magnetic field having little gradient in the X-axisdirection is formed in the clock transition space 52. On the other hand,2) when currents having the same magnitude flow in the oppositedirections through the coils 122 and 124, a uniform magnetic fieldhaving a substantially uniform gradient in the X-axis direction isformed in the clock transition space 52. When the magnitudes anddirections of currents flowing through the coils 122 and 124 areappropriately changed, a magnetic field of a linear sum of 1) and 2) isformed. Accordingly, the first coil group 120 can correct the constantterm component of the magnetic field component Bx in the X-axisdirection in the clock transition space 52, and its first order spatialderivative term in the X-axis direction.

FIG. 7 shows a second coil group 130 in the X-axis direction. The secondcoil group 130 includes two coils 132 and 134 installed apart from eachother in the X-axis direction centered in the clock transition space 52.The coils 132 and 134 are each formed to have shapes obtained bydeforming rectangular coils to have a curvature so that the coils can belaid on the same cylindrical p surface having a radius e and areconfigured so that the central angle is f, and the height in the Z-axisdirection is g. The cylindrical surface is formed to have a radiussubstantially identical to that of a cylindrical surface onto which thefirst coil group 120 in FIG. 6 is fixed. Accordingly, the relationshipe²≅(a/2)²+(c/2)² holds. The coils 132 and 134 are formed to have apoint-symmetric shape with respect to the clock transition space 52.

The second coil group 130 is a non-Helmholtz-type coil that has a shapedifferent from that of the Helmholtz coil. The coils 132 and 134 of thesecond coil group are electrically connected to each other. Currentswith the same magnitude flow through the coils in the same direction.That is, currents flow in the direction of an arrow 136 or currents flowin the direction of an arrow 138 through both the coils 132 and 134.Since the second coil group 130 is a non-Helmholtz-type coil, anon-uniform component is also generated in addition to a uniformcomponent according to a Helmholtz coil in the clock transition space 52at the center. Note that the magnitudes and the directions of currentsare the same. Accordingly, the non-uniform component is mainly a secondorder spatial derivative term component. That is, the second coil group130 can correct the constant term component of the magnetic fieldcomponent Bx in the X-axis direction in the clock transition space 52,and its second order spatial derivative term in the X-axis direction.

What controls the magnetic field component Bx in the X-axis direction inthe triaxial magnetic field correction coil 96 is basically the firstcoil group 120 and the second coil group 130 in the X-axis direction.Accordingly, these are collectively called an X-axis magnetic fieldcorrection coil. To perform correction, first, the value of the secondorder spatial derivative term in the X-axis direction is nullified bythe second coil group 130. Subsequently, adjustment of nullifying thevalue of the first order spatial derivative term in the X-axis directionand nullifying the constant term in the X-axis direction by the firstcoil group 120 is performed.

FIG. 8 shows a first coil group 140 in the Y-axis direction. The firstcoil group 140 is formed by deforming rectangular coils so as to have acurvature, and is laid on a cylindrical surface having a radius hcentered in the clock transition space 52. The first coil group includesa composite coil 142 made up of a coil 143 and a coil 144, and acomposite coil 145 made up of a coil 146 and a coil 147, the compositecoils being installed apart from each other in the Y-axis direction. Thecoils 143, 144, 146, and 147 are configured so that the central angle isi and the height in the Z-axis direction is j. The coils 143 and 144 areformed so that their edges can overlap with or be adjacent to eachother. Likewise, the coils 146 and 147 are formed so that their edgescan overlap with or be adjacent to each other. The composite coil 142and the composite coil 145 are point-symmetrically formed centered inthe clock transition space 52. The coil 143 and the coil 146, and thecoil 144 and the coil 147 are point-symmetrically formed centered in theclock transition space 52.

First, 3) a case is discussed where currents with the same magnitudeflow in the same direction through the coils 143 and 144. In this case,currents at the overlapping or adjacent configuration cancel each other,and the entire composite coil 142 serves as a single large coil.Likewise, in a case where currents with the same magnitude flow in thesame direction through the coils 146 and 147, the composite coil 145serves as a single large coil. The first coil group 140 is configured sothat the composite coil 142 and the composite coil 145 serve as a pairof Helmholtz-type coils. The Helmholtz-type coil on the cylindricalsurface shown in FIG. 8 (i.e., a Helmholtz-type coil obtained by bendingtwo rectangular coils and arranging on the same cylindrical surface) hasa central angle of about 120 degrees. No particular limitation isimposed on the length in the Z-axis direction. It is however known thatthe greater the length in the Z-axis direction is in comparison with theradius of the cylinder, the higher the magnetic field uniformly of thecentral part. The first coil group 140 can equalize the component of themagnetic field in the Y-axis direction around the center by adjustingthe direction and magnitude of the current allowed to flow.

Next, 4) the current is slightly changed from the current when theHelmholtz coil is formed. Specifically, only currents through the coil143 and the coil 147 are slightly increased in the same direction. Inthis case, the component of the magnetic field in the Y-axis directionhas the value of the first order spatial derivative term in the X-axisdirection. Note that in a strict sense, the magnetic field formed by thecoil 143 and the coil 147 has a component in the X-axis direction. Whenthe first coil group 140 is adjusted, the X-axis magnetic fieldcorrection coil is also required to be adjusted.

FIG. 9 shows a second coil group 150 in the Y-axis direction. The secondcoil group 150 shown in FIG. 9 is made up of a pair of coils 152 and 154that face each other in the Y-axis direction. Each of the coils 152 and154 is a non-Helmholtz-type coil formed to have a shape obtained bycausing a circular coil having a radius k to have a curvature, andlaying the coil on the surface of a cylinder with a radius 1 centered inthe clock transition space 52. The non-Helmholtz-type coil also formsthe second order spatial derivative term component of the magneticfield. Accordingly, the second coil group 150 is used to control theX-axis-direction second order spatial derivative term of the magneticfield component By in the Y-axis direction.

The first coil group 140 in the Y-axis direction shown in FIG. 8 and thesecond coil group 150 in the Y-axis direction shown in FIG. 9 basicallyform a Y-axis magnetic field correction coil that corrects the magneticfield component By in the Y-axis direction. The Y-axis magnetic fieldcorrection coil can correct the constant term of the magnetic fieldcomponent By in the Y-axis direction, the first order spatial derivativeterm in the X-axis direction, and the second order spatial derivativeterm in the X-axis direction.

FIG. 10 shows a first coil group 160 in the Z-axis direction. The firstcoil group 160 includes circular composite coils 162 and 165 that have aradius m and are arranged to face each other and separated by a distancen. The composite coils 162 and 165 are point-symmetric with respect tothe center. The composite coil 162 includes semicircular coils 163 and164 whose chords overlap with or are adjacent to each other. Thesemicircular coil 163 is arranged on the positive side of the X-axis,and the semicircular coil 164 is arranged on the negative side of theX-axis. Likewise, the composite coil 165 is formed by combining asemicircular coil 166 on the positive side of the X-axis and asemicircular coil 167 on the negative side of the X-axis.

The composite coils 162 and 165 are configured to have sizes and thelike so as to serve as a Helmholtz-type coil. The circular Helmholtzcoil has a relationship of m=n. The composite coils 162 and 165 areconfigured so that when currents having the same magnitude flow in thesame direction, the uniformity of the magnetic field in the Z directionaround the center is substantially equivalent to that of a Helmholtzcoil. Note that the directions and magnitudes of the currents throughthe coils 163 and 164, which constitute the composite coil 162, can bechanged freely. Accordingly, similar to the first coil group 140 in theY direction shown in FIG. 8 , the first coil group 160 can correct theconstant term and the X-axis-direction first order spatial derivativeterm of the magnetic field component Bz in the Z direction.

FIG. 11 shows a second coil group 170 in the Z-axis direction. Thesecond coil group 170 includes circular coils 172 and 174 that have aradius p and are apart by a distance q in the Z-axis direction facingeach other. The second coil group 170 is a non-Helmholtz-type coil. Thenon-Helmholtz-type coil has a non-uniform component. Accordingly, theX-axis-direction second order spatial derivative term of the magneticfield component Bz in the Z-axis direction can be corrected.

The first coil group 160 in the Z-axis direction shown in FIG. 10 andthe second coil group 170 in the Z-axis direction shown in FIG. 11basically form a Z-axis magnetic field correction coil that corrects themagnetic field component Bz in the Z-axis direction. The Z-axis magneticfield correction coil can correct the constant term of the magneticfield component Bz in the Z-axis direction, the first order spatialderivative term in the X-axis direction, and the second order spatialderivative term in the X-axis direction.

The triaxial magnetic field correction coil 96 shown in FIG. 5 is formedby controlling the X-axis magnetic field correction coil, the Y-axismagnetic field correction coil, and the Z-axis magnetic field correctioncoil in a combined manner. The triaxial magnetic field correction coil96 can correct the constant term, the X-axis-direction first orderspatial derivative term, and the X-axis-direction second order spatialderivative term of the magnetic field component Bx in the X-axisdirection. The constant term, the X-axis-direction first order spatialderivative term, and the X-axis-direction second order spatialderivative term of the magnetic field component By in the Y-axisdirection can be corrected. The constant term, the X-axis-directionfirst order spatial derivative term, and the X-axis-direction secondorder spatial derivative term of the magnetic field component Bz in theZ-axis direction can be corrected.

The triaxial magnetic field correction coil 96 performs correction ofuniformly nullifying the value of the magnetic field of the clocktransition space 52. In the case of a one-dimensional optical lattice,the clock transition space 52 is configured to have dimensions such as10 mm in the X-axis direction (the direction of the lattice), and about1 to 2 mm in the Y-axis and Z-axis directions, for example. In thisspace, for example, the error of the magnetic field is controlled so asto be within 3 μG, within 1 μG, or within 0.3 μG. The Helmholtz-typecoils and the non-Helmholtz-type coils included in the triaxial magneticfield correction coil 96 are configured to have accuracies so as to becapable of forming the magnetic field.

As shown in FIG. 4 , the triaxial magnetic field correction coil 96 isformed to have a point-symmetric shape centered in the clock transitionspace 52, and is capable of accurately correcting the magnetic field inthe clock transition space 52. However, in a macroscopic view, thecapture space 50 resides around the center of the triaxial magneticfield correction coil. Accordingly, use for correcting the magneticfield of the capture space 50 due to the MOT device is also available.That is, the current is controlled to correct the magnetic field of thecapture space 50 in a time period in which the MOT device is activatedand captures atoms from the atom beam 42. After the capture is finished,power transmission to the coil 44 for the Zeeman slower and the coil 48for the MOT device is stopped, and the magnetic field of the clocktransition space 52 is corrected. Thus, the position of the capturespace 50 is highly accurately adjusted, and the atom population can beefficiently confined in the optical lattice.

FIG. 12 shows a cylindrical holder 180 to which the triaxial magneticfield correction coil 96 is attached. The holder 180 includes circularring-shaped frames 182 and 184, and eight linear frames 186 that connectthe frames 182 and 184. The triaxial magnetic field correction coil 96is attached to the inner wall and the outer wall of the holder 180. Theholder 180 is then fixed to the rear circular wall 28 of the main body22 of the vacuum chamber 20. By attaching the triaxial magnetic fieldcorrection coil 96 to the holder 180, the efficiency of assembly andmaintenance checkup operations of the physics package 12 is improved.

The holder 180 is made of a low-permeability material such as a resin,aluminum, or the like, in order not to affect the magnetic field createdby the triaxial magnetic field correction coil 96. The holder 180 isinstalled in the main body 22 so as to be coaxial with the central axisof the cylinder of the main body 22. The holder 180 is formed to have asize close to the inner diameter of the main body 22. Accordingly, thetriaxial magnetic field correction coil 96 and the holder 180 hardlyoccupy the space in the main body 22. Note that the coils 122 and 124,which are the first coil group 120 in the X-axis direction, are attachedlinearly across the inside of the main body 22.

The holder 180 is formed to have a sparse structure using the frames.The sparse structure is a structure having many interspaces on eachsurface. The sparse structure of the holder 180 reduces the weight, andfacilitates prevention of interference with laser light that enters andis emitted from the vacuum chamber 20.

The triaxial magnetic field correction coil 96 may be, for example,entirely attached to the inner wall of the holder 180 or entirelyattached to the outer wall of the holder 180, instead of being attachedto the inner wall and the outer wall of the holder 180. In this case,for example, fixation can be easily achieved using a circularring-shaped fastener that presses the triaxial magnetic field correctioncoil 96 against the outer wall, or a circular ring-shaped fastener thatpresses the coil against the inner wall. The triaxial magnetic fieldcorrection coil 96 can be fixed to the inner wall of the main body 22without using the holder 180.

It is assumed that the triaxial magnetic field correction coil 96described above is formed by winding a covered conductor wire one ormultiple times. However, the triaxial magnetic field correction coil 96can be partially or entirely made of a flexible printed board.

FIG. 13 shows a flexible printed board developed on a plane. Acorrection coil 190 is formed on the flexible printed board. Thecorrection coil 190 includes current paths 192 that are made of aprinted electric conductor, such as copper, and contribute to formingthe magnetic field, and an insulator 194 made of a sheet-shaped flexibleresin or the like, and can be flexibly bent. Each current path 192 isconnected to a wiring path 196 provided intensively on one end. Thewiring path 196 is made of a print made of an electric conductor. Thewiring path arranges a pair where currents reciprocate, so as to beadjacent to each other, and canceled magnetic fields to be formedtherearound. The wiring path 196 is connected to a terminal connector198.

FIG. 14 shows the cylindrically bent correction coil 190 along the mainbody 22 of the vacuum chamber 20. The correction coil 190 includes aboundary part 199 where the two edges are connected to or arrangedadjacent to each other. Note that in FIG. 14 , the wiring path 196 andthe terminal connector 198 are omitted.

Similar to the triaxial magnetic field correction coil 96 where thecovered conductor wire is wound, the triaxial magnetic field correctioncoil configured with the flexible printed board is assumed to beattached to the inner wall of the cylindrical main body 22 or to thecylindrical holder 180. Note that the triaxial magnetic field correctioncoil 96 includes a current path disengaged from the cylindrical surface,besides the current path arranged on the cylindrical surface.Specifically, a side having a length a of the first coil group 120 inthe X-axis direction shown in FIG. 6 , and a linear part of the firstcoil group 160 in the Z-axis direction shown in FIG. 10 are disengagedfrom the cylindrical surface. Hereinafter, an example is described whereamong the current paths constituting the triaxial magnetic fieldcorrection coil 96, current paths arranged on the cylindrical surfaceare formed on a flexible printed board.

FIGS. 15 and 16 show an example of forming a coil at the circular partof the first coil group 160 in the Z-axis direction shown in FIG. 10using a flexible printed board. As shown in FIG. 15 , counterclockwisecurrents flowe through current paths 202 indicated by black lines, butno current flows to current paths 200 indicated by gray lines. At thistime, in consideration that the currents that are adjacent to each otherand flow in the opposite directions canceled each other, this isequivalent to a case where currents flow through virtual current paths203 shown in FIG. 16 .

FIGS. 17 and 18 show an example of forming the outermost coil of thefirst coil group 140 in the Y-axis direction shown in FIG. 8 using aflexible printed board. As shown in FIG. 17 , counterclockwise currentsflow through current paths 206 indicated by black lines, but no currentflows to current paths 204 indicated by gray lines. At this time, inconsideration that the currents that are adjacent to each other and flowin the opposite directions cancel each other, this is equivalent to acase where currents flow through virtual current paths 208 shown in FIG.18 .

As described above, on a flexible printed board, there can be formedvarious current paths that include a current path going back around theouter periphery of the cylindrical surface about the central axis of thecylinder, and a current path going back on the cylindrical surface notabout the central axis of the cylinder.

In the developed diagram as shown in FIG. 13 , on the flexible printedboard, a pattern made up of rectangular current paths can be printed.Similarly. for a correction coil 210 shown in FIG. 19 , a compositepattern that includes rectangular current paths 211 and circular currentpaths 214 can be printed. In the physics package 12, a laser light path,a vacuum-resistant optical window, and the like are provided around thewall surface of the vacuum chamber 20. Accordingly, it is effective toprovide the circular current paths 214 and prevent interference. On theflexible printed board, the coils as shown in FIGS. 16 and 18 may beformed. Multiple flexible printed boards may be used in an overlaidmanner. Thus, a part or the entirety of the triaxial magnetic fieldcorrection coil may be formed using multiple boards.

On the flexible printed board, in some cases a minute amount of gas maybe emitted from a resin of the insulator 194. Accordingly, for theinsulator 194, a material with a small amount of gas emission, such aspolyimide resin, is selected. It is conceivable that a production stepperforms a baking process at an appropriate temperature, in addition toa deaeration process, a defoaming process, a cleaning process, and thelike.

The triaxial magnetic field correction coil formed of a flexible printedboard may be installed in the vacuum chamber 20 in various forms. Forexample, it is conceivable that the triaxial magnetic field correctioncoil is installed around the inner wall of the main body 22 in a stateof being cylindrically bent, and the triaxial magnetic field correctioncoil is fixed to the main body 22 with a fastener that presses the coilagainst the main body 22. Alternatively, installation may be performedby attaching to the holder 180. Instead of the holder 180 having thesparse structure, a holder that has a dense structure with not manypores may be adopted so as to support the flexible printed board on aplane.

On the other hand, a current path disengaged from the cylindricalsurface may be separately formed using a covered conductor wire.Alternatively, by changing the structure of the holder, a current pathdisengaged from the cylindrical surface may also be created by adoptingthe flexible printed board.

In comparison with the triaxial magnetic field correction coil 96 withthe covered conductor wire being wound, the triaxial magnetic fieldcorrection coil using the flexible printed board has advantages thatfacilitate attachment to the vacuum chamber 20, as well as improvedproduction reproducibility and improved production yield.

Note that the coil shape of the triaxial magnetic field correction coilmay be variously configured in another form. For example, for each ofthe three axes, a large-sized circular coil is arranged at the middle oftwo circular coils, thus enabling formation of a Maxwell type triaxialmagnetic field correction coil. For the Maxwell type triaxial magneticfield correction coil, the components of the constant term, the firstorder spatial derivative term, and the second order spatial derivativeterm of the magnetic field can be corrected.

Furthermore, for each of the three axes, small circular coils that havea predetermined size and are provided at predetermined intervals arearranged outside of a pair of large circular coils that have apredetermined size and are provided at predetermined intervals, thusenabling formation of a tetra type axial magnetic field correction coil.The components of the constant term, the first order spatial derivativeterm, the second order spatial derivative term, and the third orderspatial derivative term of the triaxial magnetic field correction coilcan be corrected.

The axial magnetic field correction coil described above has a sphericalshape or a slightly distorted spherical shape as a whole. Accordingly,in particular, attachment to the inner wall of the substantiallyspherical vacuum chamber or therearound enables effective utilization ofthe inner space of the vacuum chamber.

FIG. 20 is a diagram corresponding to FIG. 4 , and schematically showsthe appearance and the inside of a physics package 218. Componentsidentical or corresponding to those in FIG. 4 are assigned the same orcorresponding symbols. A vacuum chamber 220 of the physics package 218is made up of a substantially spherical main body 222, and a protrudingportion 30.

In the main body 222, a triaxial magnetic field correction coil 224 madeup of circular coils is provided centered in the clock transition space52. To simplify the diagram, FIG. 20 only shows a pair of Helmholtz-typecoils in each axis direction. In actuality, one or morenon-Helmholtz-type coils are assumed to be further provided on eachaxis. The outer edge of the triaxial magnetic field correction coil 224can be configured to form a substantially spherical surface.Accordingly, by installing the triaxial magnetic field correction coil224 in the substantially spherical main body 222 around the inner wall,interference with the other components installed in the inner space ofthe main body 222 can be prevented, and design flexibility is improved.

Likewise, the triaxial magnetic field correction coil may be constructedusing square coils. Similar to the circular coils, there may be adopteda Helmholtz type triaxial magnetic field correction coil including eachpair of square coils, a Maxwell type triaxial magnetic field correctioncoil including three square coils, a tetra type triaxial magnetic fieldcorrection coil including two pair of square coils, and the like. Thesetriaxial magnetic field correction coils have a cubic shape or aslightly distorted cubic shape as a whole. Accordingly, attachment tothe inner wall or the inner wall surface of thesubstantially-cubic-shaped or substantially-cuboid-shaped vacuum chamberenables effective utilization of the inner space of the vacuum chamber.

The triaxial magnetic field correction coil may be attached to aposition closer to the clock transition space 52 than to the inner wallof the main body 22. FIG. 21 schematically shows the inside of theoptical resonator 46 shown in FIG. 1 and therearound. Note that in FIG.21 , instead of the triaxial magnetic field correction coil 96 in FIG. 1, a cubic-shaped triaxial magnetic field correction coil 230 is providedat a space between the coil 44 for the Zeeman slower and the coil 48 forthe MOT device. The cubic-shaped triaxial magnetic field correction coil230 is arranged centered in the clock transition space 52 in thecryostat reservoir 54. The cubic-shaped triaxial magnetic fieldcorrection coil 230 is formed of two pairs of coil groups made up ofsquare coils in each of the three-axis directions. One pair of the twopairs of coil groups is a Helmholtz-type coil, and the other pair is anon-Helmholtz-type coil. In a case where the magnitudes and directionsof currents are not specifically limited, the cubic-shaped triaxialmagnetic field correction coil 230 is capable of compensating themagnetic field component up to the third order spatial derivative term.Alternatively, in a case where currents having the same magnitude flowin the same direction, similar to the case of the non-Helmholtz-typecoils of the triaxial magnetic field correction coils 96 shown in FIGS.5 to 11 , the magnetic field component up to the second order spatialderivative term can be simply compensated.

In comparison with the triaxial magnetic field correction coils 96 shownin FIGS. 5 to 11 , the triaxial magnetic field correction coil 230 issignificantly small sized, and is close to the clock transition space52. Accordingly, the magnetic field formed in the clock transition space52 varies in a relatively small spatial scale. However, the triaxialmagnetic field correction coil 230, through the Helmholtz-type coil, cancompensate the constant term and the first order spatial derivative termover a relatively large range. At least the magnetic field component ofthe second order spatial derivative term can be compensated through thenon-Helmholtz-type coil. Consequently, the magnetic field of the clocktransition space 52 is uniformly nullified with sufficiently highaccuracy. Since the triaxial magnetic field correction coil 230 residesat a position close to the clock transition space 52, the current causedto flow to form the magnetic field can be significantly small, therebyachieving excellent power saving capability.

FIG. 22 is a side view from a direction A in FIG. 21 . As shown in FIG.22 , the capture space 50 is irradiated with two MOT optical beams 86 aand 86 b that are perpendicular to the Z-axis and inclined by 45 degreesfrom the X-axis and the Y-axis. Also in the direction perpendicular tothe sheet, a MOT optical beam 84 is emitted. To adjust the gradientmagnetic field formed in and around the capture space 50, a bias coil234 is arranged centered in the capture space 50. The bias coil 234includes: a pair of Helmholtz type circular coils 234 a that face eachother along the beam axis; a pair of Helmholtz type square coils 234 bthat face each other along the X-axis; and a pair of Helmholtz typesquare coils 234 c that face each other along the Y-axis. The bias coil234 corrects the gradient magnetic field to a desired distribution byadjusting the constant term component or the first order spatialderivative term component through the coils in each axis.

In the X-axis passing through the capture space 50, the optical latticelight beam 80 is emitted. The cryostat reservoir 54 including the clocktransition space 52 is provided on the optical lattice light beam 80.The triaxial magnetic field correction coil 230 is provided centered inthe clock transition space 52 around the cryostat reservoir 54. Thetriaxial magnetic field correction coil 230 includes: a coil group 230 bwhose plane has a normal in parallel with the Z-axis; and two coilgroups 230 a and 230 c whose planes have a normal perpendicular to theZ-axis and were inclined from the X-axis and the Y-axis by 45 degrees.That is, the triaxial magnetic field correction coil 230 is arranged ina state where a cubic shape along the X-axis, the Y-axis, and the Z-axisis rotated about the Z-axis by 45 degrees.

The triaxial magnetic field correction coil 230 is supported by flanges44 a and 48 a that are support members supporting the MOT device.Accordingly, the triaxial magnetic field correction coil 230 must bearranged close to the capture space 50 at the center of the MOT device.Meanwhile, the triaxial magnetic field correction coil 230 must bearranged so as to prevent interference with the MOT optical beams 86 aand 86 b passing through the capture space 50. Accordingly, the triaxialmagnetic field correction coil 230 is arranged to have a shape along theZ-axis and the MOT optical beams 86 a and 86 b.

The triaxial magnetic field correction coil 230 includes aHelmholtz-type coil and a non-Helmholtz-type coil in each axisdirection. Equalization of the magnetic field in a large space thatincludes correction of the higher order spatial derivative terms can beachieved. Accordingly, also in the X-axis direction that is thedirection of the optical lattice light beam 80, the magnetic field canbe corrected with high accuracy.

Note that the triaxial magnetic field correction coil 230 does notenclose the capture space 50. Accordingly, the magnetic field in thecapture space 50 cannot be corrected. Accordingly, as described above,the bias coil 234 that corrects the gradient magnetic field is providedin the capture space 50.

FIGS. 20 and 21 exemplify the triaxial magnetic field correction coil230 made of square coils. However, for example, coils having othershapes, such as circular coils instead of the square coils, may beadopted. For example, the cylindrical-shaped triaxial magnetic fieldcorrection coil 96 shown in FIGS. 5 to 11 may be adopted.

The triaxial magnetic field correction coil may be provided to each of aposition close to the clock transition space 52 and a position aroundthe inner wall of the main body 22. For example, it is conceivable thata Helmholtz-type coil may be provided around the inner wall of the mainbody 22, and a non-Helmholtz-type coil may be provided at a positionclose to the clock transition space 52. By providing thenon-Helmholtz-type coil at the position close to the clock transitionspace 52, a magnetic field having a large curvature can be easilycorrected.

(4) Adjustment of Magnetic Field Correction Coil

Adjustment of the magnetic field by the triaxial magnetic fieldcorrection coil is described. To correct the magnetic field, themagnetic field distribution is periodically observed around the clocktransition space 52, and when a non-uniform magnetic field distributionis identified, the currents through the triaxial magnetic fieldcorrection coil 96 are operated so as to cancel the magnetic fielddistribution. The magnetic field distribution is observed by moving theatom population confined in the optical lattice by means of the movingoptical lattice. These operations embody a situation where theindividual atoms included in the atom group are always in a zeromagnetic field.

FIGS. 23A and 23B schematically show a process of adjusting the triaxialmagnetic field correction coil. FIG. 23A shows a state of moving an atompopulation 240 confined in the moving optical lattice along the X-axis.FIG. 23B shows the relationship between the fluorescence transition andthe clock transition.

As shown in FIG. 23A, the atom population 240 is confined in thelattices sequential in the X-axis direction with a certain spatialextent. In the diagram, representative positions on the X-coordinatewhere the atom population 240 moves are represented as a position X1, aposition X2, a position X3, a position X4, and a position X5. These arepositions set in a correction space 242 set for correcting the magneticfield. The correction space 242 is set over a wide range including theclock transition space 52 that performed actual measurement. Theembodiment adopts the one-dimensional lattice with the optical latticeextending in the X-axis direction, and the atom population 240 ranges ina manner extending in the X-axis direction. It is particularly intendedto highly accurately nullify the magnetic field in the X-axis direction.The correction space 242 is set over an extent in the X-axis direction.Note that in a case where the optical lattice is formedtwo-dimensionally, it is desirable to set a correction space obtained byextending the clock transition space 52 in the two-dimensionaldirection. In a case where the optical lattice is formedthree-dimensionally, it is desirable to set a correction space obtainedby extending the clock transition space 52 in a three-dimensionaldirection.

At each position in the moved correction space 242, the atom population240 is irradiated with laser light for exciting clock transition, andthe clock transition is excited. The frequency of the laser light isswept, and the frequency of clock transition is measured at eachposition. The electron shelving method is used to observe the excitationrate of clock transition. The electron shelving method excites clocktransition and subsequently moves the atoms to a fluorescent observationspace 243. As shown in FIG. 23B, by emitting light of fluorescencetransition, the atoms emit fluorescent light 244, depending on theexcitation rate. The fluorescent light is observed by an opticalreceiver 246. The clock transition is subjected to Zeeman splittingdepending on the magnitude of the magnetic field at each position.Accordingly, the magnetic field distribution at each position isobtained from information on the Zeeman splitting. In a lower part ofFIG. 23A, the thus obtained frequency distribution is shown. Accordingto this method, the magnetic field can be measured even at a locationwhere no fluorescent light can be observed (in a cryo head etc.).Instead of the electron shelving method, a non-destructive measurementmethod using a measurement of phase shifts of atoms may be applicable tothe measurement of the excitation rate of clock transition.

FIGS. 24 and 25 are flowcharts illustrating procedures of correcting themagnetic field by the triaxial magnetic field correction coil. First,according to the procedures shown in FIG. 24 , calibration is performed.In calibration, currents in all the coils constituting the triaxialmagnetic field correction coil are stopped (set to 0 A), and thedistribution of the magnetic field in the three-axis directions aremeasured (S10). As for the magnetic field measurement, for example, themagnetic fields in the three-axis directions are measured using amagnetic sensor, such as a small-sized coil or a Hall element. Themeasured magnetic field represents the value of the background in astate where the triaxial magnetic field correction coil is not used.Next, currents having the same magnitude (1 A in FIG. 24 ) are caused toflow through all the coils (n coils), and the magnetic fielddistributions in the three-axis directions are measured using themagnetic field sensor or the like (S12 to S18). By subtracting thebackground magnetic field from the obtained magnetic field distribution,a basic magnetic field formed by the current of 1 A in each coil can beobtained.

The calibration may measure the magnetic field of the correction space242. However, the correction space 242 is in the cryostat reservoir 54.Accordingly, it is not always easy to install a magnetic sensor.Accordingly, the magnetic field may be measured adjacent to thecorrection space 242, and the magnetic field may be estimated based on aresult of an electromagnetic field simulation combined therewith. Themagnetic field may be measured in the atmosphere instead of a vacuum.Accordingly, the basic magnetic field distribution formed by each coilof the triaxial magnetic field correction coil with a current of 1 A maybe grasped. In principle, it is sufficient to perform the calibrationonce at a stage of creating the physics package 12.

Next, according to the procedures shown in FIG. 25 , the magnetic fieldis corrected. First, as described above, the atom population 240 ismoved by the moving optical lattice, and the frequency of clocktransition is measured at each position in the correction space 242(S20). The effect of Zeeman splitting is estimated, thus obtaining themagnetic field distribution in the correction space 242 (S22). Themagnetic field distribution is obtained as the absolute value of themagnetic field.

Subsequently, the current corresponding to the magnetic field to becorrected by each coil is determined using an optimization method, suchas the least squares method (S24). That is, the superimpositioncoefficient such that the magnetic field formed in the correction space242 is uniformly zero when the basic magnetic fields formed by therespective superimposed coils is obtained. Note that as described above,in the case of using both the Helmholtz-type coil and thenon-Helmholtz-type coil, first, the optimal superimposition coefficientsfor the higher order spatial derivative terms generated by thenon-Helmholtz-type coil are obtained through the least squares method orthe like. Next, the optimal superimposition for the constant term andthe first order spatial derivative term generated by the Helmholtz-typecoil is obtained by the least squares method or the like. Accordingly,calculation is simplified, and the calculation accuracy is improved. Theobtained superimposition coefficients indicate the direction andmagnitude of the current caused to flow to each coil. The obtainedcurrents are caused to flow to the triaxial magnetic field correctioncoil, thereby enabling correction of the magnetic fields of the threeaxes (S26).

The correction indicated in FIG. 25 is not necessarily frequentlyperformed under a normal condition where the magnetic field vary little.For example, in a case where clock transition is repetitively measuredin the clock transition space 52, it is sufficient to perform thecorrection shown in FIG. 25 every predetermined number of times. It isconceivable that in the case where the clock transition is measured inthe clock transition space 52, the magnitude of Zeeman splitting isalways verified, and when the magnitude becomes a predetermined value ormore, the correction shown in FIG. 25 is performed.

In a case where the magnetic field of the triaxial magnetic fieldcorrection coil is corrected for the range of the correction space 242,it is expected to stably uniformly nullify the magnetic field of theclock transition space 52, in comparison with the case for the range ofthe clock transition space 52. For example, it is conceivable that thisis because fine-scale disturbances, such as a slight fluctuation of themagnetic field, the error of magnetic field measurement, and the errorof the basic magnetic field of each coil, affect the case where only anarrow space, such as the clock transition space 52, is adopted as atarget. In actuality, in an experiment, the correction space 242 wasadopted as a target and corrected, and a result of improved accuracy wasobtained.

In the example shown in FIGS. 23A and 25 , using the moving opticallattice, the atom population 240 is moved to each place in thecorrection space 242. On the other hand, FIG. 26 schematically shows anexample of measuring the magnetic field distribution in the correctionspace 242 at one time.

In FIG. 26 , the atom population 250 is confined in the optical latticeover the entire area of the correction space 242. The fluorescent lightbeams 252 a, 252 b, 252 c, 252 d, and 252 e of the atom population 250are received at one time with spatial position information being left,by a CCD camera 254, and the frequencies are obtained. Accordingly, themagnetic field distribution of the correction space 242 is immediatelyobtained.

(5) Individual Magnetic Field Compensation Coil

As described in the aforementioned (1), for the Peltier element(refrigerator 58), which is a large current device, the individualmagnetic field compensation coil 102 for the refrigerator is provided,and compensates the magnetic field in the clock transition space 52. Forthe heater of the atomic oven 40, the individual magnetic fieldcompensation coil 104 for the atomic oven is provided, and compensatesthe magnetic field in the clock transition space 52. In a case ofcompensating the entire large stray magnetic field from the largecurrent device by the triaxial magnetic field correction coil, it isnecessary to increase the order of the triaxial magnetic fieldcorrection coil, and to increase the current. Accordingly, it iseffective to provide individual magnetic field compensation coils tocompensate the magnetic field. Here, the individual magnetic fieldcompensation coil 102 for the refrigerator is exemplified and describedin detail.

FIG. 27 schematically shows an example of configurations of the cryostatreservoir 54, the thermal link member 56, the refrigerator 58, and theindividual magnetic field compensation coil 102 for the refrigerator.The cryostat reservoir 54 is a hollow component that encloses the clocktransition space 52. Although not shown, an opening for allowing opticallattice light to pass therethrough internally is provided along theX-axis on the wall part of the cryostat reservoir 54. The cryostatreservoir 54 is made of oxygen-free copper having high thermalconductivity or the like.

The thermal link member 56 is attached to the cryostat reservoir 54. Thethermal link member 56 is a member that serves as a support structurethat supports the cryostat reservoir 54 and also as a path that removesheat from the cryostat reservoir 54. The thermal link member 56 is alsomade of oxygen-free copper having high thermal conductivity or the like.

The refrigerator 58 includes a Peltier element 58 a, a radiator plate 58b, a heat-insulating member 58 c, and permalloy magnetic field shields58 d and 58 e. The Peltier element 58 a is connected to the thermal linkmember 56, and removes heat from the thermal link member 56 with currentflowing therethrough. The radiator plate 58 b is a member made ofoxygen-free copper having high thermal conductivity or the like. Theradiator plate 58 b is provided on the outer wall of the vacuum chamber20, and radiates heat transmitted from the Peltier element 58 a to theoutside of the vacuum chamber 20.

The heat-insulating member 58 c secures the heat insulation between thepermalloy magnetic field shield 58 d and the thermal link member 56. Theheat-insulating member 58 c is made of a member, such as of silicahaving low thermal conductivity, and is spherically formed in order toreduce the number of contacts between the permalloy magnetic fieldshield 58 d and the thermal link member 56. The permalloy magnetic fieldshield 58 e is a magnetic field shield, and is made of permalloy, whichhas high thermal conductivity and high permeability. The permalloymagnetic field shield 58 e is provided between the Peltier element 58 aand the radiator plate 58 b, and transmits heat from the Peltier element58 a to the radiator plate 58 b.

A temperature sensor 260 that includes a thermocouple, a thermistor, orthe like is provided in the cryostat reservoir 54, and inputs a measuredtemperature T1 into a control device 262. A temperature sensor 264 isprovided at or around the radiator plate 58 b, and inputs a measuredtemperature T2 into the control device 262.

The control device 262 controlled current so as to keep the temperatureT1 of the cryostat reservoir 54 to a certain low temperature (e.g.,190K). The control is performed, for example, according to PID(Proportional Integral Differential) control in consideration also ofthe temperature T2 on the radiator plate 58 b side. The determinedcurrent is caused to flow to the Peltier element 58 a through a currentpath 266.

The Peltier element 58 a is a thermoelectric element that moves heatdepending on the flowing current. By causing the current to flow, thePeltier element 58 a removes heat from the thermal link member 56 (andfrom the low cryostat reservoir 54 connected to the thermal link member56) on the low temperature side, and releases the heat to the permalloymagnetic field shield 58 e (and to the radiator plate 58 b connected tothe permalloy magnetic field shield 58 e) on the high temperature side.

Through the Peltier element 58 a, a large current having, for example,about several amperes is caused to flow. Accordingly, a large magneticfield is generated. The majority of the Peltier element 58 a is coveredwith the permalloy magnetic field shield 58 d and the permalloy magneticfield shield 58 e which are of high permeability material. Accordingly,most of the generated magnetic field flows in these members, and is notleaked to the outside. However, in view of thermal conduction, amagnetic field is not allowed to be provided between the thermal linkmember 56 and the Peltier element 58 a. Accordingly, a stray magneticfield 270 is generated. The stray magnetic field 270 disturbs themagnetic field in the clock transition space 52 in the cryostatreservoir 54.

In the embodiment, the individual magnetic field compensation coil 102for the refrigerator is provided around the thermal link member 56serving as an opening portion where the magnetic field cannot beshielded. The individual magnetic field compensation coil 102 for therefrigerator generates a compensation magnetic field 272 when a currentflows.

The current is caused to flow to the individual magnetic fieldcompensation coil 102 for the refrigerator by a current path 268branched off the current path 266. That is, the Peltier element 58 a andthe individual magnetic field compensation coil 102 for the refrigeratorhave a relationship of being connected to the same current path inparallel. The electrical resistance of the Peltier element 58 a and theelectrical resistance of the individual magnetic field compensation coil102 for the refrigerator may be assumed to have constant values in atemperature environment where measurement is performed, although thevalues vary slightly. Consequently, the current that flows from thecontrol device 262 to the current path 266 is distributed to the Peltierelement 58 a and the individual magnetic field compensation coil 102 forthe refrigerator at constant ratios.

When the current flowing through the Peltier element 58 a increases, thecurrent flowing through the individual magnetic field compensation coil102 for the refrigerator increases proportionally. Accordingly, when thestray magnetic field 270 from the Peltier element 58 a increases, thecompensation magnetic field 272 generated by the individual magneticfield compensation coil 102 for the refrigerator increases in the samemanner. The individual magnetic field compensation coil 102 for therefrigerator is formed so as to compensate the stray magnetic field 270in the clock transition space 52 in the cryostat reservoir 54 (so as togenerate a magnetic field having the same magnitude in the oppositedirection) when a current having a certain magnitude flows through thecurrent path 266. Accordingly, even when the current varies, themagnetic field can be compensated. Note that the currents flow alsothrough the current paths 266 and 268. However, the reciprocatingcurrents flow close to each other through the current paths 266 and 268.Accordingly, the generated magnetic field is small, which raises noproblem.

The arrangement of the current paths 266 and 268 may be regarded ascompensation current control means for dynamically changing the currentflowing through the individual magnetic field compensation coil 102 forthe refrigerator depending on the stray magnetic field 270. Thecompensation current control means may be constructed in another manner.For example, a mode where the control device 262 causes the currentrequired by the computation to flow through the individual magneticfield compensation coil 102 for the refrigerator can be exemplified.

In the example shown in FIG. 27 , it is assumed that the individualmagnetic field compensation coil 102 for the refrigerator is formed ofone coil wound around the thermal link member 56. According to thisconfiguration, the individual magnetic field compensation coil 102 forthe refrigerator is provided adjacent to the wall of the vacuum chamber20, which can prevent the configuration around the cryostat reservoir 54from being complicated. However, no specific limitation is imposed onthe installation location of the individual magnetic field compensationcoil 102 for the refrigerator. For example, it may be installed adjacentto the cryostat reservoir 54. In a case where the individual magneticfield compensation coil 102 for the refrigerator is installed adjacentto the cryostat reservoir 54, the individual magnetic field compensationcoil 102 for the refrigerator can be reduced in size, and powerconsumption can be reduced.

The individual magnetic field compensation coil 102 for the refrigeratoris not necessarily formed of one coil, and may be formed of multiplecoils. In a case where the distribution of the stray magnetic field inthe clock transition space 52 is complicated, there is a possibilitythat use of multiple coils can relatively simply achieve compensation.

The current device, the individual magnetic field compensation coil, andthe compensation current control means constitute the magnetic fieldcompensation module. The magnetic field compensation module can achieveaccurate magnetic field compensation. Accordingly, this module isapplicable to various devices including the optical lattice clock 10.

(6) Zeeman Slower

FIG. 28 shows sectional views of the coil 44 for the Zeeman slower, andthe coil 48 for the MOT device. In the illustrated coil 44 for theZeeman slower, a coil 282 is wound around an elongatedcylindrical-shaped bobbin 280 arranged coaxially with the beam axis. Ahollow portion of the bobbin around the center is a space through whichthe atom beam 42 travels along the beam axis.

In view of functionality, the greatest part of the coil 282 constitutesa decreasing type Zeeman coil portion 284 where the number of turnsdecreases slightly from the upstream side to the downstream side of thebeam axis. The furthest downstream side of the coil 282 in the beam axisand therearound form a MOT coil portion 286 having a large number ofturns. The covered conductor wires of the Zeeman coil portion 284 andthe MOT coil portion 286 are continuously connected to each other, themagnetic field formed by the Zeeman coil portion 284 extends adjacent tothe MOT coil portion 286, and the magnetic field formed by the MOT coilportion 286 extends downstream of the Zeeman coil portion 284.Consequently, it should be noted that the boundary between the Zeemancoil portion 284 and the MOT coil portion 286 cannot be clearly defined.

On the beam-axis upstream side of the bobbin 280 there is provided adisk-shaped upstream flange 288 having a larger radius than the maximumdiameter portion of the Zeeman coil portion 284. The upstream flange 288is attached to the cylindrical wall 32 of the protruding portion 30 ofthe vacuum chamber 20. A mirror supporter, not shown, is attached to afront part of the upstream flange 288. The optical mirror 76 is attachedto the distal end of the mirror supporter.

On the beam-axis downstream side of the bobbin 280, two circularring-shaped downstream flanges 290 and 292 formed to have a diametersubstantially identical to that of the MOT coil portion 286 areprovided. The downstream flange 290 is formed to have a circular ringshape that is relatively thick along the beam axis direction, and isprovided around the boundary between the Zeeman coil portion 284 and theMOT coil portion 286. The downstream flange 292 is formed to have acircular ring shape that is relatively thin along the beam axisdirection, and is provided downstream of the MOT coil portion 286. Theupper parts of the downstream flanges 290 and 292 are attached to anupper support member 312, and the lower parts of the flanges areattached to a lower support member 314. The upper support member 312 andthe lower support member 314 are attached to the rear circular wall 28of the main body 22 of the vacuum chamber 20.

The coil 48 for the MOT device is arranged downstream of the coil 44 forthe Zeeman slower by a predetermined distance. In the coil 48 for theMOT device, a MOT coil 302 is wound around a short cylindrical-shapedbobbin 300 provided coaxially with the beam axis. On the beam-axisupstream side of the bobbin 300, a thin circular ring-shaped flange 304having a diameter substantially identical to that of the MOT coil 302 isprovided. On the beam-axis downstream side of the bobbin 300, arelatively thick circular ring-shaped flange 306 having a diametersubstantially identical to that of the MOT coil 302 is provided. Theupper parts of the flanges 304 and 306 are attached and fixed to theupper support member 312.

In the coil 44 for the Zeeman slower, the bobbin 280, the upstreamflange 288, and the downstream flanges 290 and 292 are made of copper orthe like, which has high thermal conductivity and low permeability. Thebobbin 280, the upstream flange 288, and the downstream flanges 290 and292 are combined to each other by welding to have high strength and tobe in close contact.

In the coil 44 for the Zeeman slower, more coil is wound around on thebeam-axis upstream side. The upstream side has a larger weight than thedownstream side. By combining the upstream flange 288 with thecylindrical wall 32 of the protruding portion 30 of the vacuum chamber20, the coil 44 for the Zeeman slower is stably arranged in the vacuumchamber 20.

In the coil 44 for the Zeeman slower, heat is generated by the currentflowing through the coil 282. The vacuum chamber 20 is in a vacuum.Unlike the atmosphere, thermal conduction via a gas does not occur.Accordingly, in the coil 44 for the Zeeman slower, a small coolingeffect due to blackbody radiation occurs. However, the heat of the coil282 is mainly required to be removed by thermal conduction via a solid.The bobbin 280 is in contact with the coil 282, and heat is effectivelytransferred from the coil 282. The upstream flange 288 and thedownstream flanges 290 and 292 have a large area in contact with thecoil 282, and remove heat from the coil 282. As shown in FIG. 2 , theupstream flange 288 is connected to the cooler 92 for the Zeeman slowerat the cylindrical wall 32 of the protruding portion 30. In the cooler92 for the Zeeman slower, cooling water is circulated in a water-coolingtube made of copper or the like, thereby cooling the upstream flange288. Thus, excessive increase in temperature of the coil 44 for theZeeman slower is prevented.

The bobbin 300 and the flanges 304 and 306 of the coil 48 for the MOTdevice also have high thermal conductivities, and are made of copper orthe like having low permeability. The bobbin 300, and the flanges 304and 306 are combined with each other by welding to have high strengthand to be in close contact. The MOT coil 302 of the coil 48 for the MOTdevice is of smaller size and lighter weight than the coil 282 of thecoil 44 for the Zeeman slower. The entire coil 48 for the MOT devicealso has a light weight. Accordingly, the coil 48 for the MOT device isstably attached to the rear circular wall 28 via the upper supportmember 312 to which the flanges 304 and 306 are fixed.

The current caused to flow is smaller and the amount of heat generationis smaller in the MOT coil 302 of the coil 48 for the MOT device than inthe coil 282 of the coil 44 for the Zeeman slower. The peripheries ofthe MOT coil 302 in three directions of the coil 48 for the MOT deviceare enclosed by the bobbin 300 and the flanges 304 and 306. Accordingly,the heat generated by the MOT coil 302 is transmitted to the cooler 94for the MOT device via the upper support member 312. It is assumed thata cooling scheme is adopted for the cooler 94 for the MOT device.However, in a case where the heat quantity to be removed is small, anair cooling scheme may be adopted.

In the example in FIG. 28 , the number of turns of the coil 282decreases roughly monotonically. However, in detail, irregularities areformed in the beam axis direction. One reason for providing theirregularities is to obtain a desired magnetic field intensity at aspecific position on the beam axis. For example, in the capture space 50that captures atoms, the magnetic field is required to be zero. Anotherreason may be to adopt a configuration of causing no magnetic field atpositions where no magnetic field is required, in view of power saving.It is sufficient that the coil 44 for the Zeeman slower generates amagnetic field necessary to decelerate atoms or confine atoms. A reasonfor providing irregularities may be a request for mechanical support orthermal radiation. The weight of the coil increases with the number ofturns. Accordingly, it becomes difficult to support. Furthermore, theheat discharge from the coil increases. Accordingly, it is conceivableto increase the number of turns of the coil of a portion advantageousfor support, or a portion having a high heat radiation efficiently. Inthe example shown in FIG. 28 , the coil 282 of the coil 44 for theZeeman slower is formed to have a relatively convex shape where thenumber of turns is large at a portion in contact with the upstreamflange 288, and have a relatively concave shape where the number ofturns is relatively small on the downstream side. Accordingly, thebarycenter of the coil 44 for the Zeeman slower moves toward theupstream flange 288, and fixation by the upstream flange 288 is stable.The contact area between the coil 282 and the upstream flange 288 islarge, and thermal conduction is effectively achieved from the coil 282to the upstream flange 288.

Here, by reference to FIG. 29 , a void in the coil is described. FIG. 29shows sectional views of upper parts of two Zeeman coils 320 and 330. Inthe Zeeman coil 320, the number of turns monotonically decreases in thebeam axis direction including a portion 322. On the other hand, in theZeeman coil 330, the number of turns is locally small at a portion 332called a void. However, in the Zeeman coil 330, the number of turns islocally large before and after the portion 332 in the beam axisdirection. Accordingly, the distribution of the magnetic field createdby the entire Zeeman coil 330 is substantially equal to the distributionof the magnetic field created by the Zeeman coil 320.

The way of forming the coil shape at and around the void can betheoretically obtained. The magnetic field distribution generated by aunit component follows the Biot-Savart law. Conversion from the magneticfield distribution to the current distribution can be dealt with as thedeconvolution method, or the inverse problem in a general perspective.The method of obtaining a solution of a minimum current path through theinverse problem is described, for example, in Mansfield P, Grannell PK.“NMR diffraction in solids.” J Phys C: Solid State Phys 6: L422-L427,1973. However, it is obvious that there are some multiple roots only ifthere is no restriction to the minimum current. In FIG. 29 , providedthat the solution of the minimum current path satisfying a desiredmagnetic field distribution is the Zeeman coil 320, the Zeeman coil 330with the increased current density around the void could also form adesired magnetic field distribution.

As for the coil 282 shown in FIG. 28 , the downstream flange 290 isprovided at the middle of the coil 282. This means that the downstreamflange 290 is provided at the large void. Before and after thedownstream flange 290 in the beam direction, the numbers of turns isconfigured to be greater than in a case without the downstream flange290, thus removing or reducing the adverse effects of the downstreamflange 290.

FIG. 30 shows the magnetic field distribution at the coil 44 for theZeeman slower and the coil 48 for the MOT device. The x axis representsthe position on the beam axis. The origin corresponds to the capturespace 50. The y axis represents the magnitude of the magnetic field onthe beam axis. The coil 44 for the Zeeman slower and coil 48 for the MOTdevice are formed symmetrically with respect to the beam axis.Accordingly, the magnetic field on the beam axis only has a component inthe beam axis direction. On the beam axis, a position where the coil 282of the coil 44 for the Zeeman slower is arranged, and a position wherethe MOT coil 302 of the coil 48 for the MOT device is arranged areindicated. Points on the graph indicate calculated values of themagnetic field. Narrow lines indicate the value of the magnetic fieldthat is ideal for decelerating atoms toward the capture space 50 by theZeeman slower.

The magnetic field becomes the maximum slightly downstream of the end ofthe coil 282 on the upstream side. On the slightly upstream side of theposition of the maximum value, the value of the magnetic field abruptlydecreases. On the further upstream side, the value gradually approacheszero. The ideal magnetic field has a distribution where the magneticfield outside of the coil 282 becomes zero, and no magnetic field leaksto the outside. However, generation of the magnetic field due to thecurrent has a spatial extension. For example, in a case without anopposite directional coil compensating (canceling) the external magneticfield, the magnetic field outside of the coil 282 cannot be entirelyzero.

On the downstream side of the position with the magnetic field of themaximum value, the magnetic field monotonically decreases. The number ofturns of the coil has slight irregularities as described above. Themonotonically decreasing magnetic field for Zeeman slower is created bythe effect of the surrounding coil. The magnetic field having thegradient substantially coincides with the ideal magnetic fielddistribution for Zeeman slower, and indicates steady deceleration ofatoms toward the capture space 50.

The magnetic field abruptly decreases before the end of the downstreamside of the coil 282. The MOT coil part 286 therearound has a largenumber of turns. No coil resides on the further downstream side.Accordingly, the value of the magnetic field rapidly decreases.

The magnetic field decreases with a substantially constant slope, andbecomes zero in the capture space 50. Furthermore, the magnetic fielddecreases with the same slope, and becomes the minimum value (thenegative value became strongest) around the MOT coil 302 of the coil 48for the MOT device. This is because the MOT coil 302 causes the currentto flow in the direction opposite to the coil 282. A portion rangingfrom a portion around the MOT coil part 286 of the coil 282 to a portionaround the MOT coil 302 approximately forms a Helmholtz-type coil.Accordingly, by causing the current to flow through the MOT coil 302 inthe opposite direction, the magnetic field having a constant slope isallowed to be formed. Although not shown, the magnetic field having aconstant slope is formed also in a direction perpendicular to the beamaxis. The gradient magnetic field formed by the MOT device is irradiatedwith MOT optical beams in the respective three axes. Accordingly, theatoms are allowed to be captured in the capture space 50 at the origin.On the downstream side of the MOT coil 302, the magnetic field graduallyapproaches zero.

As described above, the coil 44 for the Zeeman slower and the coil 48for the MOT device are installed in the combined manner, and the lengthin the beam axis direction is allowed to be reduced in comparison with acase where the Zeeman slower and the MOT device are separately provided.The entire coil length can also be reduced, which could facilitate powersavings and reduction in amount of heat generation.

Note that in a case where a background magnetic field is present, theposition where the magnetic field is zero deviates from the capturespace 50. Accordingly, in the process of capturing the atoms, thetriaxial magnetic field correction coil 96 or a bias coil for correctingthe gradient magnetic field is adjusted, thus allowing generation of thecompensation magnetic field that cancels the background magnetic fieldaround the capture space 50.

Next, by reference to FIGS. 31A and 32B, an example of an increasingtype coil 340 for a Zeeman slower is described. FIG. 31A is a sectionalview showing a state before the coil 340 for the Zeeman slower isattached to the inside of the vacuum chamber 20. FIG. 31B is a sectionalview showing a state after the attachment. A coil 342 of the coil 340for the Zeeman slower shown in FIG. 31A serves as the Zeeman coilportion 344 whose greater part of the beam-axis upstream side has afunction of a Zeeman coil. The furthest downstream side of the coil 342serves as a MOT coil portion 346 where the function of the Zeeman coiland the function of the MOT coil reside in a combined manner. At theZeeman coil portion 344, the number of turns monotonically increasesfrom the end of the upstream side to the downstream side. Around the endon the downstream side, irregularities are repeated, and subsequentlythe number of turns becomes the maximum on the most downstream side. Forthe sake of convenience, a portion with the maximum number of turns andtherearound is called the MOT coil portion 346. As described above, inview of functionality, the portion also plays a role of a Zeeman coil.

The coil 340 for the Zeeman slower internally includes a bobbin. Aflange 350 is provided at the end on the upstream side. A flange 352 isprovided at the middle of the coil 342 around the end on the downstreamside. A flange 354 is provided on the end on the downstream side. Theflanges 350, 352 and 354 are welded to the bobbin.

A mirror supporter, not shown, is attached to the furthest upstreamflange 350. The optical mirror 76 is fixed to the mirror supporter.

The downstream flanges 352 and 354 are linked to each other at portionsother than the bobbin, and improve the strength. The flange 352 is alarge disk that is thin and has a large radius. The flange 352 isattached to a circular ring supporter 370 made to have a ring shape. Thering of the circular ring supporter 370 internally includes awater-cooling tube 372 through which cooling water flows, and cools thecoil 342 through the flange 352. Right and left beams 374 are attachedto an upper portion of the circular ring supporter 370. Right and leftbeams 376 also serving as water-cooling tubes are attached to a lowerpart of the circular ring supporter 370. The beams 374 and 376 areattached to the rear circular wall 28 of the main body 22 of the vacuumchamber 20, and support the entire part including the coil 340 for theZeeman slower. The beams 374 and 376 serve as exhaust heat paths fortransmitting heat of the coil 342 to the rear circular wall 28. Notethat cooling water flowing through the beams 376 is allowed to becirculated to the radiator plate 58 b of the refrigerator 58.

This configuration assumes that a coil 380 for the MOT device isattached to the rear circular wall 28 by a separately provided supportmember. The coil 340 for the Zeeman slower is assumed to be positionedwith the coil 380 for the MOT device by a positioning mechanism.

FIG. 32 is a diagram corresponding to FIG. 30 , and shows the magneticdistribution in a case where the increasing type coil 340 for the Zeemanslower and the coil 380 for the MOT device are adopted. The magnetismgradually increases from the downstream side of the coil 342 of the coil340 for the Zeeman slower, and becomes the maximum value before the MOTcoil part 346. The increase in magnetism well coincides with a targetcurve required to achieve the Zeeman slower. On the downstream side ofthe position with the maximum value, the magnetism rapidly decreases.Before and after the capture space 50 serving as the origin, themagnetism decreases from positive to negative at a substantiallyconstant slope, and becomes zero in the capture space 50. The magneticfield becomes the minimum around the coil 380 for the MOT device, andsubsequently gradually approaches zero.

At a portion constituting the MOT device before and after the capturespace 50, the slope of the magnetic field becomes abrupt in comparisonwith the case of the decreasing type in FIG. 30 . This is because thenumber of turns of the MOT coil 346 at the coil 342 is large, and thenumber of turns of the facing coil 380 for the MOT device is also large.By making the slope of the magnetic field steep, atoms can be capturedwith a short distance in the beam axis direction.

The increasing type coil 340 for the Zeeman slower shown in FIG. 32 canhave a shortened length as compared with the decreasing type coil 44 forthe Zeeman slower in FIG. 30 . This is because the increasing type canefficiently decelerate atoms. The increasing type can suppress themagnetic field required to decelerate the atoms and achieve powersavings in comparison with the decreasing type.

On the other hand, in the increasing type coil 340 for the Zeemanslower, the side of the capture space 50 is heavier. Accordingly, it isdifficult to support the coil in the vacuum chamber 20. The increasingtype has the greater number of turns on the capture space 50 side.Accordingly, problems are caused in that the amount of heat generationis a large amount of heat generation around the center of the vacuumchamber 20 and it is difficult to cool. However, as described above, thecoil 340 for the Zeeman slower is supported around the center of thevacuum chamber 20 by the circular ring supporter 370 having the coolingfunction. Accordingly, these problems are not caused.

The mode of attaching the increasing type coil 340 for the Zeeman slowershown in FIGS. 31A and 31B is only an example. Another mode may beadopted. By reference to FIGS. 33A and 33B, a modified example isdescribed.

FIG. 33A is a perspective view showing a state before the coil 390 forthe Zeeman slower is attached to the inside of the vacuum chamber 20.FIG. 33B is a perspective view showing a state after the attachment. Acoil 392 of the coil 390 for the Zeeman slower is wound in a mannersimilar to that of the coil 340 for the Zeeman slower. The configurationincluding a bobbin and flanges 394, 396, and 398 is also almost thesame. However, in the coil 390 for the Zeeman slower, the shape of theflange 396 provided close to the lower end in the beam direction is asemicircular shape that is substantially about the lower half. A portionthat supports the flange 396 serves as a substantially U-shapedsemicircular ring supporter 400 obtained by halving a circular ring. Thesemicircular ring supporter 400 is provided with a water-cooling tube402.

In the mode shown in FIGS. 33A and 33B, the flange 396 has asemicircular shape. The cooling performance in a case where the coolingwater circulation is equivalent decreases slightly. On the other hand,in the coil 390 for the Zeeman slower, a space is present above theflange 396. Accordingly, in the vacuum chamber 20, access is facilitatedfrom the optical resonator 46 toward the atomic oven 40. Presence of thespace above the semicircular ring supporter 400 facilitates removal ofthe optical resonator 46. Furthermore, since the distance of thewater-cooling tube in the vertical direction is reduced, the disturbanceof the flow caused by convection in the water-cooling tube can be easilyprevented. Note that the flange 396 shown in FIGS. 33A and 33B can beappropriately provided pores in its surface. In the case of providingthe pores, the efficiency of thermal conduction decreases, but reductionin weight can be achieved. Likewise, the flange 352 shown in FIGS. 31Aand 31B could be appropriately provided with pores in its surface.

FIG. 34 is a sectional view of a coil 410 for an increasing type Zeemanslower according to another embodiment. The coil 410 for the Zeemanslower included a bobbin 412 having a thickness varying in the beamdirection. The cylindrical-shaped bobbin 412 has a constant innerdiameter, but an outer diameter that gradually decreases stepwise fromthe upstream to the downstream in the beam direction. A coil 414 woundaround the bobbin 412 has a greater number of turns on the downstreamside in the beam axis direction. Accordingly, the outer diameter of thecoil 414 is substantially constant in the beam axis direction.

According to the configuration shown in FIG. 34 , increase in the outerdiameter of the bobbin 412 increases the contact area between the bobbin412 and the coil 414. Accordingly, the thermal conduction efficientlyfrom the coil 414 to the bobbin 412 improves. A covered conductor wirecan be wound using the steps of the bobbin 412, thus facilitatinginstallation of the coil 414.

Note that this embodiment is not necessarily limiting; instead of around wire having a round section, a rectangular flat wire having arectangular section may be used for the covered conductor wire includedin the coil 414, which can further improve the thermal conductionefficiently with the bobbin 412 and the like. As described below, in acase where the periphery of the coil 414 is covered with a thermalconductive cover, the outer diameter of the coil 414 is constant, whichfacilitates bringing the cover into close contact with the coil 414, andremoving heat through the cover.

The example of installing the Zeeman slower in the vacuum chamber 20 hasbeen described so far. The cooling mechanism of removing Joule heatcaused by the coil is provided, which enables thermally stableinstallation of the Zeeman slower in the vacuum chamber 20. Hereinafter,as another example, an example of sealing part or the entirety of thecoil with a cover (i.e., encapsulation) is described.

FIGS. 35A and 35B are side sectional views showing a coil 420 for aZeeman slower and a cover 440. FIG. 35A shows a state before the cover440 is attached to the coil 420 for the Zeeman slower. FIG. 35B shows astate after the attachment. The coil 420 for the Zeeman slower is of thedecreasing type, where the number of turns of the coil graduallydecreases in the beam axis direction.

A bobbin 422 of the coil 420 for the Zeeman slower is provided with aflange 424 at the end of the upstream side of the beam axis, and alsowith a flange 426 at a middle position on the downstream side. Similarto the example described above, the bobbin 422 and the flanges 424 and426 are made of copper or the like, which secures high thermalconductivity. The outer periphery of the flanges 424 and 426 areprovided respectively with sealing members 428 and 430 made of indium.The sealing members 428 and 430 are formed to have a ring-shaped,relatively thin sheet shape, or a ring-shaped thick shape. Indium has acharacteristic enabling achievement of stable vacuum sealing even withlarge temperature variation. The flange 426 is provided with a hermeticconnector 432 that is a vacuum-resistant connector.

A coil 434 is wound around the bobbin 422 between the flange 424 and theflange 426. A coil 436 is wound on the downstream side of the flange426. The coils 434 and 436 are each formed of a covered conductor wireincluding copper insulated with a resin. The coil 434 and the coil 436are electrically connected via the hermetic connector 432.

The cover 440 is formed to have a cylindrical shape. The cover 440 ismade of copper, which is the same as that of the bobbin 422, the flanges424 and 426, and the coils 434 and 436, and prevents deformation due tothermal expansion.

The cover 440 is installed for coverage from the flange 424 to theflange 426. That is, part of the inner periphery of upstream end of thecover 440 encloses part of the outer periphery of the flange 424, and issealed with the sealing member 428. Part of the inner periphery ofdownstream end of the cover 440 encloses part of the outer periphery ofthe flange 426, and is sealed with the sealing member 430. The cover 440is formed so as to have a positive tolerance from the length from theflange 424 to the flange 426, and can securely enclose both the flanges.

The atmospheric pressure can be freely set in the cover 440 only if thesealing members 428 and 430 can securely achieve shieling. For example,air at the atmospheric pressure may be enclosed, or a roughly pumpedvacuum may be used. The roughly pumped vacuum is a state of beingrarefied using a turbopump or the like, and is set to about 1 to 0.1 Pa,for example. In the case where the inside of the cover 440 is theroughly pumped vacuum, the pressure difference between the inside andthe outside of the cover 440 is small in a state where the vacuumchamber 20 is in a vacuum. Accordingly, the sealing surfaces by thesealing members 428 and 430 can be strongly prevented from beingseparated from each other.

An inert gas, such as nitrogen or helium, may be enclosed in the cover440. A gas having low reactivity with a resin used for the coil when thecoil 434 is at a high temperature is selected as the inert gas. Thepressure of the inert gas is not specifically limited, and may be oneatmosphere, or a roughly pumped vacuum. The inside of the cover 440 maybe filled with, for example, a lightweight resin, such as urethane foam.In this case, the strength of the cover 440 can be improved.

The coil 420 for the Zeeman slower becomes a high temperature due toJoule heat during energization. The coil 434 with the larger number ofturns generates more Joule heat than the coil 436 with the smallernumber of turns. Accordingly, the coil 434 tends to become a hightemperature. When the temperature becomes higher, a minute amount of gas(this gas is called outgas) contained in the resin of the coveredconductor wire included in the coil 434 is discharged. However, in thecoil 420 for the Zeeman slower, the coil 434 is sealed by the bobbin422, the flanges 424 and 426, and the cover 440. Accordingly, no outgasleaks into the vacuum chamber 20. This prevents an error of the clocktransition that would otherwise be caused by the outgas. Consequently,the coil 420 for the Zeeman slower sealed by the cover 440 functions asa vacuum installation coil having high usability in a case ofinstallation in a vacuum.

The cover 440 also serves as a thermal conduction medium between theflange 424 and the flange 426. That is, thermal conduction between theflange 424 and the flange 426 is not only through the bobbin 422 butalso through the cover 440. Accordingly, there is also an advantageouseffect of cooling the coils 434 and 436.

The above description assumes that the cover 440 covers the outerperipheries of the flanges 424 and 426, but is not in contact with thecoil 434. However, the cover 440 may be in contact with part or theentirety of the outer peripheral surface of the coil 434. In this case,heat from the coil 434 is directly transferred to the cover 440, whichimproves the heat radiation efficiently. In particular, in the casewhere the coil 414 has a constant outer diameter as with the coil 414shown in FIG. 34 , it is easy to achieve close contact with the innerperiphery of the cover 440. If it is difficult to form a shape bringingthe cover 440 into contact with the outer peripheral surface of the coil434, a thermal conductive member may be inserted between the cover 440and the coil 434.

In the embodiment shown in FIGS. 35A and 35B, the coil 434 is notcovered with the cover 440. This is because the number of turns of thecoil 434 is small, and the necessity of addressing outgas discharge islow. The coil 434 is a portion including the MOT coil included in theMOT device, and the optical resonator 46 and the like are arrangedadjacent to this portion. Accordingly, increase in diameter due tocoverage of the coil 434 with the cover is prevented. However, ifinterference with the surrounding devices and components can be avoided,the entire part including the coil 434 may be covered with the cover andencapsulated.

In the example in FIGS. 35A and 35B, the decreasing type coil 420 forthe Zeeman slower is exemplified. However, even in the case of theincreasing type, part or the entirety of what includes a portion havingthe large number of turns can be encapsulated.

Note that the above description assumes that the cover 440 is in closecontact with the flanges 424 and 426 using the indium sealing members428 and 430, and the inside is made hermetic. Alternatively, sealingmembers made of another material instead of indium may be adopted. Inthe case of using the sealing members, the cover 440 may be detachablyattached to the flanges 424 and 426 using fixation screws, for example.Alternatively, for example, the cover 440 and the flanges 424 and 426may be brought into close contact with each other by a semipermanentsealing method, such as welding or vacuum brazing, and the inside may bemade hermetic.

The above description exemplifies the optical lattice clock. However,those skilled in the art can apply each technology of this embodiment toother than the optical lattice clock. Specifically, the technology isalso applicable to atomic clocks other than the optical lattice clock,and an atom interferometer that is an interferometer using atoms.Furthermore, this embodiment is applicable also to various types ofquantum information processing devices for atoms (including ionizedatoms). Here, the quantum information processing devices are devicesthat perform measurement, sensing, and information processing using thequantum states of atoms and light, and may be, for example, a magneticfield meter, an electric field meter, a quantum computer, a quantumsimulator, a quantum repeater, and the like besides an atomic clock andan atom interferometer. The physics package of the quantum informationprocessing device can achieve miniaturization or transportability byusing the technology of this embodiment, similar to the physics packageof the optical lattice clock. It should be noted that in such devicesthe clock transition space is not a space for clock measurement but issometimes dealt with simply as a space for causing clock transitionspectroscopy.

In such device, for example, by providing the triaxial magnetic fieldcorrection coil according to the embodiment, improvement in the accuracyof the device can possibly be achieved. By providing the three axesaccording to the embodiment in the vacuum chamber, miniaturization,transportability, or improvement in accuracy of the physical package canpossibly be achieved. Furthermore, by introducing the magnetic fieldcompensation module, the magnetic field distribution can be controlledwith high accuracy. In the physics package using the vacuum chamber,installation of the vacuum installation coil is effective.

In the above description, for facilitating understanding, the specificaspects are described. However, these exemplify the embodiments, and maybe variously embodied in other modes.

Hereinafter supplements of the embodiments are described.

(Supplement 1)

A magnetic field compensation module, including:

a current device that is provided in a vacuum chamber that encloses aclock transition space in which atoms are arranged, and allows currentfor the device to flow therethrough and generates a stray magneticfield;

a compensation coil that is provided adjacent to the current device, andallows current for the coil to flow therethrough; and

control means for dynamically changing current for the coil that is toflow through the compensation coil, and compensates the stray magneticfield with respect to the clock transition space.

(Supplement 2)

The magnetic field compensation module according to supplement 1,

wherein the current device is a Peltier element that cools an isothermalcryostat reservoir that maintains the clock transition space at apredetermined low temperature, and the control means changes the currentfor the coil in accordance with the temperature of the isothermalcryostat reservoir, or current for the device that is to flow throughthe Peltier element.

(Supplement 3)

The magnetic field compensation module according to supplement 1,

wherein a magnetic field shield made of a high permeability material isprovided around the current device, and

the compensation coil compensates the stray magnetic field straying fromthe magnetic field shield.

(Supplement 4)

The magnetic field compensation module according to supplement 1,

wherein the control means includes a distributor wire that distributesthe current for the coil from the current for the device, anddistributes the current for the coil in accordance with the current forthe device.

(Supplement 5)

A physics package system for an optical lattice clock, the systemincluding the magnetic field compensation module according to supplement1.

(Supplement 6)

A physics package system for an atomic clock, the system including themagnetic field compensation module according to supplement 1.

(Supplement 7)

A physics package system for an atom interferometer, the systemincluding the magnetic field compensation module according to supplement1.

(Supplement 8)

A physics package system for a quantum information processing device foratoms or ionized atoms, the system including the magnetic fieldcompensation module according to supplement 1.

(Supplement 9)

A physics package system, including:

the magnetic field compensation module according to supplement 1; and

at least one atomic laser cooling technology device among a Zeemanslower, a magneto-optical trap, and an optical lattice trap that guidethe atoms into the clock transition space.

(Supplement 10)

A physics package, including:

a vacuum chamber; and

a Zeeman slower that includes a bobbin that is formed to have acylindrical shape and allows an atom beam to flow along a beam axis inthe cylinder, and a series of coils wound around the bobbin, and forms amagnetic field caused to have a spatial gradient in the cylinder,

wherein the bobbin is provided with a flange at which an outer surfaceof the cylinder is radially enlarged at an intermediate position in adirection of the beam axis,

the series of coils are wound around the bobbin beyond the flange, and

the Zeeman slower is installed in the vacuum chamber so that the flangeis attached directly or indirectly to the vacuum chamber.

(Supplement 11)

The physics package according to supplement 10,

wherein the series of coils is of an increasing type where the number ofturns is greater on a downstream side than that on an upstream side ofthe atom beam, and

the flange is provided on the downstream side of the bobbin.

(Supplement 12)

The physics package according to supplement 11,

wherein the vacuum chamber is formed to have a substantially cylindricalshape having a central axis in parallel with the beam axis, and

the flange is attached to a cylindrical wall on a downstream side of theatom beam in the vacuum chamber, indirectly using a support member.

(Supplement 13)

The physics package according to supplement 12,

wherein the flange is formed to have a substantially circular shape,

the support member includes a substantially circular ring-shapedsupporter that supports an outer edge of the flange, and

the substantially circular ring-shaped supporter is provided with acooling mechanism that flows a liquid coolant through a tube and coolsthe flange.

(Supplement 14)

The physics package according to supplement 12,

wherein the flange is formed to have a substantially sectoral shapebeing enlarged along a direction including a vertically downwardcomponent,

the support member includes a substantially U-shaped supporter thatsupports an outer edge of the flange, and

the substantially U-shaped supporter is provided with a coolingmechanism that flows a liquid coolant through a tube and cools theflange.

(Supplement 15)

The physics package according to supplement 10,

wherein the bobbin and the flange are made of a metal, and

the physics package is provided with a cooling mechanism that directlyor indirectly cools the flange.

(Supplement 16)

The physics package according to supplement 10, further including

an opposite coil wound around the beam axis at a position apart on adownstream side of the atom beam from the Zeeman slower,

wherein the series of coils and the opposite coil form a MOT magneticfield between the series of coils and the opposite coil.

(Supplement 17)

A physics package for an optical lattice clock, the package includingthe physics package according to supplement 10.

(Supplement 18)

A physics package for an atomic clock, the package including the physicspackage according to supplement 10.

(Supplement 19)

A physics package for an atom interferometer, the package including thephysics package according to supplement 10.

(Supplement 20)

A physics package for a quantum information processing device for atomsor ionized atoms, the package including the physics package according tosupplement 10.

(Supplement 21)

A vacuum installation coil, the coil including:

a coil that is installed in a vacuum chamber, is wound around a beamaxis in which an atom beam flows, and forms a magnetic field caused tohave a spatial gradient; and

a sealing member that hermetically encloses part or an entirety of thecoil.

(Supplement 22)

The vacuum installation coil according to supplement 21,

wherein the sealing member is made of a metal.

(Supplement 23)

The vacuum installation coil according to supplement 21,

wherein the sealing member includes:

a cylindrical shaped bobbin which is provided on an inner peripheralside of the coil and around which the coil is wound;

two flanges that are enlarged outer surfaces of the cylinder of thebobbin, and enclose side surfaces of the coil in a direction of the beamaxis; and

a cover that encloses an outer peripheral side of the coil between thetwo flanges.

(Supplement 24)

The vacuum installation coil according to supplement 23,

wherein the cover encloses at least part of outer peripheries of the twoflanges.

(Supplement 25)

The vacuum installation coil according to supplement 23,

wherein the cover is in direct contact with part or an entirety of anouter peripheral side of the coil, or in indirectly contact therewithvia a thermally conductive member inserted into a space enclosed by thesealing member.

(Supplement 26)

The vacuum installation coil according to supplement 21,

wherein the number of turns of the coil varies in a direction of thebeam axis, and

a range enclosed by the sealing member includes a portion having themaximum number of turns in the coil.

(Supplement 27)

The vacuum installation coil according to supplement 21,

wherein a space enclosed by the sealing member is kept more rarefiedthan an atmosphere.

(Supplement 28)

The vacuum installation coil according to supplement 21,

wherein an inert gas is enclosed in a space enclosed by the sealingmember.

(Supplement 29)

The vacuum installation coil according to supplement 21,

wherein a space enclosed by the sealing member is filled with a foamedresin.

(Supplement 30)

The vacuum installation coil for an optical lattice clock according tosupplement 21,

wherein the sealing member includes a vacuum-resistant connector, and

wherein a portion of the coil hermetically enclosed by the sealingmember and a not enclosed portion are electrically connected through thevacuum-resistant connector.

(Supplement 31)

A physics package, including:

the vacuum installation coil according to supplement 21; and

a vacuum chamber.

(Supplement 32)

The physics package according to supplement 31,

wherein the coil is a decreasing type coil having a relatively smallnumber of turns on a downstream side of the atom beam,

the physics package includes an opposite coil wound around the beam axisat a position apart on a downstream side of the atom beam from thedecreasing type coil,

the decreasing type coil and the opposite coil form a gradient magneticfield for a MOT device between the decreasing type coil and the oppositecoil, and

the sealing member hermetically encloses a portion including a furthestupstream side of the beam axis in the coil, and does not enclose aportion including a furthest downstream side.

(Supplement 33)

The physics package according to supplement 31,

wherein the coil is an increasing type coil having the relatively largenumber of turns on a downstream side of the atom beam,

the physics package includes an opposite coil wound around the beam axisat a position apart on a downstream side of the atom beam from theincreasing type coil,

the increasing type coil and the opposite coil form a gradient magneticfield for a MOT device between the increasing type coil and the oppositecoil, and

the sealing member hermetically encloses a portion including a furthestdownstream side of the beam axis in the coil.

(Supplement 34)

A physics package for an optical lattice clock, the package includingthe physics package according to supplement 31.

(Supplement 35)

A physics package for an atomic clock, the package including the physicspackage according to supplement 31.

(Supplement 36)

A physics package for an atom interferometer, the package including thephysics package according to supplement 31.

(Supplement 37)

A physics package for a quantum information processing device for atomsor ionized atoms, the package including the physics package according tosupplement 31.

(Supplement 38)

A sealing member sealing a coil that is installed in a vacuum chamber,is wound around a beam axis in which an atom beam flows, and forms amagnetic field caused to have a spatial gradient,

wherein an area between the sealing member and the coil side is sealedwith indium formed to have a ring sheet shape or thick shape, andhermetically encloses part or the entirety of the coil.

REFERENCE SIGNS LIST

-   -   10 optical lattice clock, 12 physics package, 14 optical system        device, 16 control device, 18 PC, 20 vacuum chamber, 22 main        body, 24 cylindrical wall, 26 front circular wall, 28 rear        circular wall, 30 protruding portion, 32 cylindrical wall, 34        front circular wall, 38 leg, 40 atomic oven, 42 atom beam, 44        coil for Zeeman slower, 44 a flange, 46 optical resonator, 48        coil for MOT device, 48 a flange, 50 capture space, 52 clock        transition space, 54 cryostat reservoir, 56 thermal link member,        58 refrigerator, 58 a Peltier element, 58 b radiator plate, 58 c        heat-insulating member, 58 d, 58 e permalloy magnetic field        shield, 60 vacuum pump main body, 62 vacuum pump cartridge, 64,        66 vacuum-resistant optical window for optical lattice, 68        vacuum-resistant optical window for MOT light, 70, 72        vacuum-resistant optical window for MOT light, 74, 76 optical        mirror, 80 optical lattice optical beam, 82 Zeeman slower        optical beam, 84, 86 a, 86 b MOT optical beam, 90 cooler for        atomic oven, 92 cooler for Zeeman slower, 94 cooler for MOT        device, 96 triaxial magnetic field correction coil, 98        vacuum-resistant electric connector, 102 individual magnetic        field compensation coil for refrigerator, 104 individual        magnetic field compensation coil for atomic oven, 120 first coil        group, 122, 124 coil, 130 second coil group, 132, 134 coil, 136,        138 arrow, 140 first coil group, 142 composite coil, 143, 144        Coil, 145 composite coil, 146, 147 coil, 150 second coil group,        152, 154 coil, 160 first coil group, 162 composite coil, 163,        164 coil, 165 composite coil, 166, 167 coil, 170 second coil        group, 172, 174 coil, 180 holder, 182, 184, 186 frame, 190        correction coil, 192 current path, 194 insulator, 196 wiring        path, 198 terminal connector, 199 boundary portion, 200, 202,        203, 204, 206, 208 current path, 210 correction coil, 212, 214        current path, 218 physics package, 220 vacuum chamber, 222 main        body, 224, 230 triaxial magnetic field correction coil, 240 atom        population, 242 correction space, 243 fluorescent observation        space, 244 fluorescent light, 246 optical receiver, 250 atom        population, 252 a, 252 b, 252 c, 252 d, 252 e fluorescent light,        254 CCD camera, 260 temperature sensor, 262 control device, 264        temperature sensor, 266 current path, 268 current path, 270        stray magnetic field, 272 compensation magnetic field, 280        bobbin, 282 coil, 284 Zeeman coil part, 286 MOT coil part, 288        upstream flange, 290, 292 downstream flange, 300 bobbin, 302 MOT        coil, 304, 306 flange, 312 upper support member, 314 lower        support member, 320 Zeeman coil, 322 portion, 330 Zeeman coil,        332 portion, 340 coil for Zeeman slower, 342 coil, 344 Zeeman        coil part, 346 MOT coil part, 350, 352, 354 flange, 370 circular        ring supporter, 372 water-cooling tube, 374, 376 beam, 380 coil        for MOT device, 390 coil for Zeeman slower, 392 coil, 394, 396,        398 flange, 400 semicircular ring supporter, 402 water-cooling        tube, 410 coil for Zeeman slower, 412 bobbin, 414 coil, 420 coil        for Zeeman slower, 422 bobbin, 424, 426 flange, 428, 430 sealing        member, 432 hermetic connector, 434, 436 coil, 440 cover.

1. A triaxial magnetic field correction coil provided in a vacuumchamber that encloses a clock transition space in which atoms arearranged, the triaxial magnetic field correction coil compromising: ashape configured to correct any of a constant term, a first orderspatial derivative term, a second order spatial derivative term, and athree or higher order spatial derivative term, or any combination of theterms.
 2. A physics package, comprising: the triaxial magnetic fieldcorrection coil according to claim 1; and the vacuum chamber.
 3. Thephysics package according to claim 2, wherein the vacuum chambercompromises an inner wall formed to have a point-symmetric shapecentered in the clock transition space in a first axis among the threeaxes, and the triaxial magnetic field correction coil comprises a groupof coils that is formed to have a point-symmetric shape centered in theclock transition space in a direction of the first axis, and is arrangedon the inner wall or adjacent to the inner wall.
 4. The physics packageaccording to claim 3, wherein the triaxial magnetic field correctioncoil comprises two or more groups of coils that have different coilsizes, coil shapes, or distances in the first axis.
 5. The physicspackage according to claim 3, further comprising a holder that has asparse structure and is detachably attached around the inner wall of thevacuum chamber, wherein the group of coils is attached to the holder. 6.The physics package according to claim 3, wherein the vacuum chamber isformed to have a point-symmetric shape centered in the clock transitionspace in a second axis that is an axis other than the first axis amongthe three axes, and the triaxial magnetic field correction coilcomprises group of coils that is formed to have a point-symmetric shapecentered in the clock transition space in a direction of the secondaxis, and is arranged on the inner wall or adjacent to the inner wall.7. The physics package according to claim 6, wherein the vacuum chamberis formed to have a point-symmetric shape centered in the clocktransition space in a third axis that is an axis other than the firstaxis and the second axis among the three axes, and the triaxial magneticfield correction coil comprises a group of coils that is formed to havea point-symmetric shape centered in the clock transition space in adirection of the third axis, and is arranged on the inner wall oradjacent to the inner wall.
 8. The physics package according to claim 3,wherein the vacuum chamber is formed to have a substantially cylindricalshape allowing the clock transition space to be disposed on a centralaxis of the cylinder.
 9. The physics package according to claim 3,wherein the vacuum chamber is formed to have a substantially sphericalshape allowing the clock transition space to be disposed at a center ofthe sphere.
 10. The physics package according to claim 3, wherein atleast a pair of walls of the vacuum chamber that face each other havesubstantially square shapes, and the clock transition space is formed tohave a substantially rectangular shape arranged on an axis connectingcenters of the pair of walls.
 11. The physics package according to claim3, wherein at least part of the group of coils are formed on a flexibleprinted board, and are attached to the inner wall formed to have thepoint-symmetric shape or to a holder formed to have a point-symmetricshape around the inner wall.
 12. The physics package according to claim2, further comprising: a pair of MOT coils that are provided in thevacuum chamber, form a gradient magnetic field, and capture atoms in acapture space of the MOT device; a bias coil that is provided in thevacuum chamber, and is for generating a bias magnetic field at aposition where the atoms are captured; and movement means for moving theatoms captured in the capture space to the clock transition space by amoving optical lattice, wherein at least part of the triaxial magneticfield correction coil is supported by a supporter that supports the MOTcoils.
 13. The physics package according to claim 2, wherein an opticalresonator that comprises an optical mirror that forms an optical latticeis provided around the clock transition space in the vacuum chamber, andat least part of the triaxial magnetic field correction coil is providedin the optical resonator.
 14. The physics package according to claim 2,wherein at least part of the triaxial magnetic field correction coil areprovided around an inner wall of the vacuum chamber.
 15. A physicspackage system, comprising: the physics package according to claim 2;and a control device that controls current that flows to the triaxialmagnetic field correction coil.
 16. The physics package according toclaim 2, wherein the physics package is for an optical lattice clock.17. The physics package according to claim 2, wherein the physicspackage is for an atomic clock.
 18. The physics package according toclaim 2, wherein the physics package is for an atom intweferometer. 19.The physics package according to claim 2, wherein the physics package isfor a quantum information processing device for atoms or ionized atoms.20. The physics package according to claim 2, further comprising atleast one atomic laser cooling technology device among a Zeeman slower,a magneto-optical trap, and an optical lattice trap that guide the atomsinto the clock transition space.